SURVEY OF MOSQUITOES Of MASSACHUSETTS REPORT 1 940 SURVEY OF MOSQUITOES OF M A Q Q A r M ! i C f T TQ i v ! t~\ >—\ j i — v—) L_ ! 1 v—s FINAL REPORT !9 40 MASSACHUSETTS DEPARTMENT Or PUBLIC HEALTH IN COOPERATION WITH THE WORK PROJECTS ADMINISTRATION COMMONWEALTH OF / M AS 5 A C H U 5 E I T 5, / DEPARTMENT OF PUBLIC HEALTH PAUL J. JANMAUH, M . t\, CO M M I S S IO N £ R AND FEDERAL WORKS AGcNCY WORK P RCJECT5 ADMlNlST RATION DENIS W DELANEY A 0 M I N I S T R AT O H A SURVEY OF THE MOSQUITOES OF MASSACHUSETTS WITH A DISCUSSION OF THE RELATION OF MOSQUITOES TO DISEASE COMPILED BY VLADO A. GETTING, M.D.,DR.P.H. TECHNICAL DIRECTOR MOSQUITO SURVEY UNDER THE DIRECTION OF ROY F. F£EM5TER,M,D.,DR.P,H DIRECTOR % DIVISION OF COMMUNICABLE DISEASES 1940 WILLIAM A. HOG A N . P RO J ECT SUPERVISOR I PREFACE Paul J. Jaamauh, IhD. Commissionei of Public Health This edition of an abbreviated report is being made available for limited distribution uo those interested in the outstanding results of the mosquito survey carried out in Massachusetts in the simmer of 1839. In evaluating the figures given in the report, it must be constantly kept in mind that they are largely qualitative and not quantitative. They represent not so much an indication of the comparative number of mosquitoes found in the various communities but are rather a measure of the diligence of the collectors and the cooperation of the boards of heal'd* and other local organisations. As a result the communities which gave greater assistance in supplementing the collections made by the W.P.A. personnel would appear at first glance to have a greater and abundance of mcsouitces than those A *** in which the collections were only by the regular collectors. The number and organizations who aided in this survey are too numerous to refer this preface, but references to tnem will be found in various portions of the report itself. Suffice it to say that the success of the project depended upon the cooperation of all those concerned and the splendid results obtained arc evidence of that cooperation. This survey has collected more information concerning mosquitoes than is available in regard to any other comparable area in the country. The facts obtained will make more intelligent planning of control measures possible in the future, whether to eliminate mosquitoes as a pest or to guard the pop- ulation against the spread of disease. II INTRODUCTION As a result of the outbreak of equine encephalomyelitis in 1933. the Massachusetts Department of Public Health decided than plans should be made to prevent the disease in the future. A committee called together by Dr. Paul Jakmauh, Commissioner of Public Health, considered the problem in detail and decided that the most pressing need was complete information in regard to the most probable vector, the mosquito. At the urgent request of the Commassioner, Governor Leverett Sal tonstall presented the following message to the General Court of Massachusetts: HOUSE „ , . . NO. 2181 The Commonwealth of Massachusetts Executive Department, State House,Poston,April 12, 1939, To the Honorable Senate and House of Representatives: House Bill Ko, 399, A resolve providing for an in- vestigation by the Department of Pu.blic Health, in co- operation with the Federal Works Progress Administra- tion, relative to the varieties and prevalence of certain kinds of mosquitoes in the Commonwealth of Massachusetts. calls for an appropriation in the aggregate of 117,500. This sum will bo the Commonwealth’s contribution to the cost of the investigation and will permit the Department of Public Health to investigate in co-operation with the Federal Works Progress Administration, trie prevalence and the seasonal and geographical distribution of mosquitoes throughout the Commonwealth, Last summer there was an epidemic of eucep.lialomyoJ.itis in certain parts of our Commonwealth. This is an extremely dangerous disease to young people and there is -considerable fear among the- authorities that there may be a recurrence of this epidemic in the coming summer months, Work'with relation to mosquitoes, to bo effective, must be done, in the month of May, I, therefore, recommend this .appropriation•to be made in advance of the budget. Leverett Saltonstall. Governor of the Commonwealth, III On May 9th, the Department of Public Health was authorized to jonduct the Survev by the following resolve: (Chap. 14) RESOLVE PROVIDING FOR AIT INVESTIGATION OF THE DEPART- MENT OF PUBLIC HEALTH, IN CO-OPERATION WITH THE FED ■ ERAL WORKS PROGRESS ADMINISTRATION, RELATIVE TO THE VARIETIES AND PREVALENCE OF CERTAIN HINDS OF MOSQUI- TOES IN THE COIJMOMEALTH OF MASSACHUSETTS Resolved, That the department of public health is hereby authorized to investigate, in co-operation with the Federal llorks Progress Administration or its suc- cessor, the prevalence and the seasonal and geograph- ical distribution of mosquitoes throughout the common- wealth.For said purpose said department may expend for services, other than services of said Federal llorks Progress Administration or its successor, and for trav- eling expenses, supplies, materials and equipment, a sum not exceeding seventeen thousand five hundred dol- which sum is hereby appropriated from the Gener- al Fund or ordinary revenue of the commonwealth in ad- vance of final action on the general appropriation bill, pursuant to a recommendation of the governor to that effect. Said department shall repent its recom- mendations, if any, together with drafts of legisla- tion necessary to carry such recommendations into effect., by filing the same with the clerk of the house of rep- resentatives on or before the first Wednesday of Decem- ber in the year nineteen hundred and forty. Approved May 9, 19390 One month later, the Work. Projects Administration approved the expendi- ture of federal funds and the Survey was officially started on June 12th. This investigation was an activity of the Division of Communicable Diseas- es of the Department of Public Health and was node with the cooperation of the 1-7ork Projects Administration which furnished a personnel of one hun- dred fiftyo Collections were started on June 22nd and continued through December 8th, 1939. About 15$ of the specimens were submitted by volun- teer collectors who were enrolled through cooperating boards of health and other interested agencies. The Director of the Division of Communicable Diseases, Roy F, Feemster, DUD., Dr. P.H. and the Technical Director of the Mosquito Sur- vey, Ylado A. Getting, M.D., Dr. P.E. planned the organization of the Survey in March 1939. The latter has continued to devote the larger portion of his time to this investigation, has directed the technical work and has compiled' the final report. The entire 77. P. A, personnel Y/as under the direction of the Project Supervisor, William A. Hogan. This report is an account of the findings of the investigations made during the Survey„ It is divided into three parts; IV Part Ore Mosquito-borne Diseases in Massachusetts Part Two The Administration of tho Mosquitc Survey Part Throe Massachusetts Mosquitoes The first part is an analysis of the 1938 outbreak of equine encephalomyel- itis, of malaria, of other mosquito-borne diseases which are prevalent or may become prevalent in tho state and of their control. The second part is a description of tho organization of the project and of the methods used in the collection, recording said analysis of data. The third part is a record of the facts collected by tho Survey and the conclusions which were made con- cerning equine encephalomyelitis and malaria as a result cf these findings. Collections of mosquitoes were made throughout the Commonwealth by the person1 nel of the Survey, In some areas volunteers greatly increased the number of specimens submitted for identification. From Cape Coo. and several other a- reas, many more collections were submitted through the cooperation of Mosqui- to Control Projectso Theso increased collections do not indicate uhat mos- quitoes wore more numerous. As a. matter of record, mosquitoes were often less numerous in these areas and tho larger number of specimens warn a result of more extensive and thorough collecting. V TABJE OF CONTENTS Preface Introduction Table of Contents Index of Tables -III Index of Charts x Index of Maps Miscellaneous Index H SERVEY OF MOSQUITOES OF MASSACHUSETTS CHAPTER I Equine Encephalomyelitis | Varieties of Equine Encephalomyelitis 1 Experimental Mo&quite Transmission 2 Other Methods of Transmission 3 Conclusions of Transmission' 5 II The Massachusetts Outbreak of Equine Encephalomyelitis Epidemiology ® Analysis of Cases in Man 1938 Mosquito Survey Objectives of the 1939 Survey III Other Mosquito-Borne Diseases Malaria Mortality Statistics Morbidity Statistics Malaria Acquired in Massachusetts Yellow Fever Dengue Filariasis Equine Encephalomyelitis Lymphocytic Choriomeningitis Poliomyelitis St. Louis Encephalitis IV The Control of Mosquito-Borne Diseases 20 - 90 Mosquito Control Protection from Mosquitoes 21 Immunization of Susceptibles 22 Removal of Sources of Infection 22 Prevention of Entry into Hew Areas 22 P'Z Conclusion . . 24 V Organization State Personnel Work Projects Administration Personnel 2-6 Office 26 Field 26 Volunteer Collections 2® VI TAPLE OF CONTENTS VI Collection of Specimens 31 Collection Points 31 Survey of Collection Point 32 Daily Work of Field Personnel 32 VII Technical Procedures 35 Identification of Specimens 35 Identification Key 3-6 Special Mosquito' Collections 36 VIII Analysis of Data 38 Posting Shoots 38 Punch Card Analysis 38 Town Code 46 Collection Point Code 46 Checking 46 IX Sampling the Mosquito Population 47 Duration of State-Wide Survey 47 Mosquito Collections 47 Specimens Collected 53 Collections Per Square Mile 53 Population Effects on Mosquito Collections 55 X Meteorological Conditions and Mosquitoes 58 Rain 58 Temperature 61 Wind 64 XI Mosquito Breeding Places 65 XII The Collection of Adult Mosquitoes 77 Biting Habits 77 Environment 80 XIII Vectors of Equine Encephalomyelitis 83 numerical Importance of Vectors 83 Biting Habits 89 Distribution by Watersheds 89 XIV Vectors of Malaria 91 numerical Importance 91 Biting Habits 93 Distribution by Drainage Areas 94 XV Mosquitoes of Massachusetts 95 Genera 95 Seasonal Distribution of Genera 97 Species 99 VII 0F_CONTESTS Geographical Distribution 102 Seasonal Distribution 104 Relation to Population Density 112 Public Health Importance 114 Aodes atropalpus 114 A, aurifer 115 A, canadensis 115 A,, cant at or 115 A, cinereus 116 A0 communis 117 A, dorsalis 117 A excrucians 117 A. fitchii 117 A, hirsuteror. 117 A, impiger 116 A. implacabilis 118 A, intruders -18 A. punctor 118 A, sollicitans 118 A. stimulans 118 A. tacniorhynchus 119 a, trichurus 120 A, uriseriatus 121 A, trrvittatus 121 A0 vexans 122 Anopheles crucians 125 A, maculipennis 123 A. punctipennis 123 A, quadriinaculatus 123 A, walker! 124 Culex apicalis -^24 C, pipiens 124 0, salinarius 125 C, territans 125 Mansonia perturbans 125 Orthopodomyia signifera Psorophora ciliata 12‘& F, Columbia© 128 P* posticata 126 Theobaldia impatiens 128 T. inornata 128 T. melanura 126 T, morsitans 128 Uianotaenia sapphirina 126 Wyeomyia smithii 127 Chaoborus species 127 Corethrella 127 Dixa spocica 127 Eucorethra underwoodi 127 Mochionyx species 128 VIII TABLE OF CONTENTS XVI Conclusions on the Mosquito Transmission of Equine Encephalomyelitis 129 XVII S urnmary 132 Mosquito-Borne Diseases in Massachusetts 132 The Administration of the Mosquito Survey 135 Massachusetts Mosquitoes 134 INDEX OF TABLES TABLE I Mosquito Vectors of Equine Encephalomyelitis 2 II Disease with Proved and Suspected Mosquito Transmission 10 III Application of Control Methods to Mosquito-Borne Diseases 21 IV Summary of Mosquito Collections '49 V Mosquito Collection, Adults, Larvae and Percent Distribution 51 VI Relation of Population to Total Mosquito Collections, All Communities 55 VII Relation of Population to Total Mosquito Collections, Communities with Routine Collections Only 55 VIII Direction of Ire vailing Winds -64 IX Mosquito Breeding Places at Regular Collection Points 65 X Regular Collections of Larvae in Different Types of Breeding Places -66 XI Character of Water in Natural Water Bodies 68 XII Collections of Vector Larvae from Bodies of Water Different in Character 69 XIII Character of Bottom in Natural Water Bodies 70 XIV Collections of Vector Larvae from Bodies of Water with Different Bottoms 71 XV Kinds of Vegetation in Natural Water Bodies 72 XVI Collections of Vector Larvae from Bodies of Water with Different Vegetation 73 XVII Kinds of Vegetation at Edge of Natural Water Bodies 74 XVIII Collections of Vector Larvae from Breeding Places with Different Vegetation at Water-Edge 75 XIX Larval Associates 76 XX Adult Mosquitoes Caught on Man 77 XXI Adult Mosquitoes Caught in Houses 78 XXII Adult Mosquitoes Caught on Man and in Houses 79 XXIII Adult Mosquitoes Caught in Barn and Stable 80 XXIV Association of Vector Adults with Different Types of Terrain 81 XXV Association of Vector Adults with Different Types of Trees 82 XXVI Numerical Importance of Vectors of Equine Encephalomyelitis by Specimens 83 IX INDEX OF TABLES (continu ed) TABLE XXVII Numerical Importance of Vectors of Equine Encephalomyelitis By Collections S3 XXVIII Number of specimens per Collection* Vectors of Equine Encephalomyelitis 84 XXIX Vectors of Equine Encephalomyelitis, Percent 01 Collections of Larvae which were Vectors 84 XXX Vectors of Equine Encephalomyelitis, Percent of Collections of Adults which were Vectors 86 XXXI Vectors of Equine Encephalomyelitis, Percent of Adult Specimens which were Vectors 87 XXXII Vectors of Equine Encephalomyelitis, Distribution of Drain- age Areas, Humber of Collections CO XXXIII Vectors of Malaria, Distribution of Species and Counties 91 XXXIV Vectors of Malaria, Distribution in Drainage Areas by Collections 93 XXXV Relative Importance of the Genera of Massachusetts Mosqui- toes, Percent of Adults and Larvae by Specimens 95 XXXVI Relative Importance of the Genera of Massachusetts Mosqui- toes, Percent of Adults and Larvae by Collections 97 XXXVII Average Humber of Specimens per Collection 99 XXXVIII Mosquitoes of Massachusetts 100 XXXIX Mosquitoes of Massachusetts by Counties 102 XL A Seasonal Distribution by Weeks, Number of Collections Larvae 104 XL B Seasonal Distribution by Weeks, % of Total Collections Larvae 108 XLI A Seasonal Distribution by Weeks, Number of Collections Adults 108 XLI B Seasonal Distribution by Weeks, % of Total Collections Adults 110 XL1I A Collection of Larvae in Relation to Population Density 112 XLII B Collection of Adults in Relation to Population Density 113 XLIII Summary of Mosquitoes of Massachusetts 137 X INDEX OF CHARTS FIGURE I Seasonal Incidence of Equine Encephalomyelitis in Massachusetts 1938 8 II Number of Towns in which Collections were Made, By Meeks 43 III Number of Collections, By Meeks 50 IV Adult Mosquitoes, Percent of Total Collections By Meeks of Year, Massachusetts 1939 52 V Adults and Larvae, Number of Specimens By Meeks, Massachusetts 1939 54 VI Distribution of Cities and Towns by Number of Mosquito Collections per Square Mile 53 VII Relation of Mosquito Collections to Rainfall, Massachusetts 1939 * 59 VIII Accumulation of Daily Deviation From Normal, Massachusetts 1938-1939 “ 60 IX Precipitation, Massachusetts 1938 & 1939 61 X Relation of Rainfall to Deaths in Horses Due to Eastern Variety of Equine Encephalomyelitis Virus, Massachusetts 1958 " 1 62 XI Accumulation of Daily Deviation From Normal in Fahrenheit Degrees, Massachusetts 1958 63- XII Mosquito Collection By Genera, Massachusetts 1939 96 XIII Aedes, Anopheles & Culex Seasonal Distribution, Percent of Collections 98 XIV Aedes atropalpus. Seasonal Distribution 114 XV Aedes cantator. Seasonal Distribution 116 XVI Aedes sollicitans, Seasonal Distribution 119 XVII Aedes taeniorhynchus. Seasonal Distribution 120 XVIII liedes triseriatus. Seasonal Distribution 121 XIX Aedes vexans. Seasonal Distribution 122 INDEX OF MAPS MAP 1 Distribution of Equine Encephalomyelitis, Massachusetts 1938 S II Distribution of Proved Experimental Vectors of Equine Encephalomyelitis, Eastern Type 85 III Main Drainage Areas of Massachusetts 88 IV Vectors of Malaria 92 V Cases of Equine Encephalomyelitis, Massachusetts 1939 130 MISCELLANEOUS INDEX ITEM Organization Chart 25 Code for Summary Sheet 39 Punch Card Collection Point Code 41 Punch Card Town Code 44- 1 CHAPTER I EQUINE ENCEPHALOMYELITIS The Mosquito Survey was organized as a result of the 1938 out- break of equine encephalomyelitis among humans, animals, and birds in southeastern Massachusetts* The outbreak constituted the first time that the disease was recognized in this State; moreover, it was the first time that equine encephalomyelitis was demonstrated to infect species other than horses and mules. Equine encephalomyelitis is a newly recognized in- fectious virus disease. Comparatively little is known of this virus which has a broad host selectivity. Its economic importance, however, is great, as it kills thousands of horses and mules every year. Laboratory experi- ments have demonstrated that many species of small mammals and birds are susceptible, IVith its recognition among humans, the disease has become a great unsolved problcm;a problem which requires study in an effort to ar- rive at some method for its control. The mosquito has been proved to be able to transmit the disease experimentally, but, as yet, the role of the mosquito as a natural vector of equine encephalomyelitis has not been established. The objectives of the Mosquito Survey wore to collect and determine the various species of mosquitoes present in Massachusetts; to obtain data on the geographical distribution and the seasonal predominance of the different species; to ascertain the possible relationship of these mosquitoes to certain dis- eases which are transmitted by those insects; and, in particular, to es- tablish whether the presumptive vectors of equine encephalomyelitis are true or merely laboratory vectors. VARIETIES OF EQUINE ENCEPHALOMYELITIS Equine encephalomyelitis is a disease which may be due to one of4 four different varieties of virus. However, the clinical picture produced by each variety ranges from a mild and subacute form to one which is fulminating and acute. Similarly, the varieties may be separated by their immunological and serological charac- teristics. In the United States,only the western and eastern varieties are known to occur. The western is limited to the area west of the Appalach- ian Mountains; epizootics of this variety among horses have been charac- terized by a high attack rate, a low fatality rate, raid a subacute form of this disease. The eastern variety, on'the other hand., has been known to oc’cur only along the Atlantic seaboard. In 1939, both the eastern , . and western varieties were isolated in Alabama, Epizootics of the eastern variety arc characterized by a low attack rate, a high fatal- ity rate, and a more acute and fulminating type of disease. Both var- ieties have been demonstrated to infect humans. However, since.only a few cases of the disease have been recognized, it.is impossible to describe the characteristics of infection with these varieties in man. Neverthe- less, with the information on hand, it seems likely that the western var- iety of this disease in man may be in many instances, sub-clinical or mild, whereas the eastern variety causes an acute and fulminating type of disease not unlike that in horses. 2 EXPERIMENTAL MOSQUITO TRANSMISSION The first successful laboratory trans- mission of equine encephalomyelitis by the bite of a mosquito was made by Kelser in 1933. This investigator, after many unsuccessful attempts was able to transmit the virus of western variety by the bite of the tropical Aedes aegypti mosquito. During an epizootic of a similar disease along the Chesapeake Bay coast line. Ten Eroeck and Merrill observed that cases occurred on farms which were separated by more than ten miles and between which there had been no contact. Moreover, those cases due to the eastern variety were limited to a peculiar geographical distribution. Upon fur- ther investigation, they found that this distribution was like that of the common salt marsh mosquito, Aedes sollicitans. The following year, Mer- rill, Lacaillade and Ten Broeck were able to transmit both the eastern and western varieties to laboratory animals by the bite of this salt marsh mos- quito, The significance of this mosquito transmission with the local mos- quito whose distribution corresponded to that of the outbreak was at once apparent. During the 1935 outbreak of equine encephalomyelitis in Mary- land, Giltner and Shahan triturated in saline and injected into numerous guinea pigs 1,300 mosquitoes of various species collected from a region attacked by the disease. All these experiments were negative. However, with our present knowledge of viruses, it has become evident that these experiments wore inconclusive, as the virus in the triturated mosquitoes was dead by the time the experiments were performed. TABLE I LICSQUITO VECTORS OF EQUINE ENCEPHALOMYELITIS Name of Mosquito 77 e stern Eastern Occurrence Variety Variety in Mass, Acdcs aegypti X X 0 A. sollicitans X X X A, cantutor X X X A, vexans X X X 'A. triscriatus X X A, atropalpus X X A, taeniorhynchus X X X A, dorsalis X X A, albopictus X 0 A, nigromaculis X 0 Many investigators have experimented with the mosquito trans- mission of this disease. At first, these experiments were difficult to interpret, due to the varying conditions under which they were performed. At the present time, there are seven species of mosquitoes which have been demonstrated experimentally to transmit the eastern variety virus to lab- oratory animals. The western variety has been transmitted by eight species of mosquitoes. In all instances of transmission, the mosquito concerned belonged to the genus Aedes. Transmission experiments with the other gen- era of mosquitoes, Culex, Anopheles, TheoLaldia, Mansonia, Hyeomyia and Uranotacnia, have thus far been negative. Table I gives a summary of the transmission experiments. It is apparent that some mosquitoes have been shown to transmit one variety of the virus but not the other. So far as is known, there is no biological reason why any species of mosquitoes 3 should be able to transmit one variety of equine encephalomyelitis virus and not the other. It is believed that eventually experiments will show that if a species can transmit one variety, it can also transmit the oth- er, In all, there arc ten species of Aedcs mosquitoes which have trans- mitted the virus experimentally; but it is likely that they arc not of e- qual importance as vectors. Further investigation is needed to determine which species arc natural vectors and which are the important ones* OTHER METHODS OF TRANSMISSION A discussion of the epidemiology of oquine encephalomyelitis would not be complete without mention of other experi- mental and field data. Laboratory experiments repeated by various workers have demonstrated that equine encephalomyelitis is not transmitted by di- rect contact. Susceptible animals, which were caged with infected ones, failed to contract the disease in spite of the intimate contact. Field ob servations during epizootics revealed that multiple infections of horses in the same stable or on the same farm were rare. The evidence is, there- fore, against infection by direct contact. In 1936, Syverton and Berry demonstrated that Dermacentor andersoni, the Rocky Mountain wood tick, was capable of transmitting ex- perimentally the western variety. The continuity of the virus through all stages in the development cycle of the'tick, including survival through the egg stage, was definitely demonstrated. There is in ticks, therefore, a potential vrector and reservoir, especially during the winter months when cases of equine encephalomyelitis are rare and the ticks are hibernating. Besides ticks and mosquitoes, experiments on other potential in- sect vectors have been made, especially on those that habitually bite hor- ses and mules, Riley studied the insect transmission of disease due to filterable viruses and concluded that the stable fly, Stomoxys calcitrons, the horsefly, Tabanus punctifer, and the hornfly, Haomatobia serrata, were not capable of being vectors of equine encephalomyelitis. CONCLUSIONS ON TRAJISMISSIOIT The seasonal occurrence of equine encephalo- myelitis during the middle of summer and early autumn, and the sudden end of the outbreak with the arrival of killing frosts, strongly support the laboratory evidence of insect transmission. Although there is no evidence that infection in nature is caused by mosquitoes or ticks, both of these are potential vectors. The theory of mosquito transmission merely awaits confirmation by the finding of naturally infected mosquitoes. The proof of mosquito transmission of yellow fever required thirty years; and it is probable that some time may elapse before the mosquito is finally estab- lished as the true vector of e’quino encephalomyelitis. In a disease with a broad host selectivity such as equine enceph alomyelitis, it is not unlikely that the reservoir of the disease may be found in one or more animals, Syverton and Berry suggested that small rodents, the,gopher in particular, which they found susceptible in experi- ments, may'be the reservoir. Ten Broeck suggested that birds may be the reservoirs. Several investigators have carried out experiments on the susceptibility of birds and animals to oquine: encephalomyelitis• Recent- ly, Davis has demonstrated that the eastern variety virus remains in the circulating blood of birds for a period of three or four days. These birds rarely showed more than mild symptoms, and .continued .their feeding 4 as though they were perfectly well. These findings suggest that birds may be the natural host of the disease and that the disease has been re- cently introduced to horses, which have no natural immunity to the dis- ease, The recognition of the occurrence of the disease in man is most recent. Thus far, all infections of man have occurred during the epi- zootics of the disease in horses; and it is likely that human infections may be an overflow phenomenon of the disease from the natural hosts dur- ing pandemics of the disease. BIBLIOGRAPHY Davis, Wm, A,; Experiments on the Role of Birds and Mosquitoes in the Epidemiology of Equine Encephalomyelitis, J, Bact, 39: 42, 1940 Giltner, L, T,; Shahan, M. S,; The Immunological Relationship of eastern and TITestern Strains of Equine Encephalomyelitis Virus, Sc, 78: 587-588 1933 Kelser, -R, A,; Mosquitoes as Vectors of the Virus of Equine Encephalo- myelitis,- J, Am, Vet, Med, Assn, 82: 767'-771, 1933 Merrill, M, H,j Lacailladc, C, W,; Ten Brooch, C,; Mosquito Transmission of Equine Encephalomyelitis. Sc. 80: 251-252, 1934 Riley, Wm, A,; The Role of Insects and Allied Forms in the Transmission of Diseases Due to Filterable Viruses, Minn, Mod, 21; 817-821, 1938 Syverton, J, T,; Berry, G, P,; The Tick as'a Vector for the Virus Disease, Equine Encephalomyelitis, J, Bact. 33: 60, 1937 Syverton, J, T,; Berry, G, P.; An Arthropod Vector for Equine Encephalo- myelitis, Western Strain, Sc, 84: 186-187, 1936 Ten Broeck, C,; Merrill, Transmission of Equin'c Encephalomyelitis by Acdcs aogypti. Arch, Path, 20; 164, 1935 Ten Broeck,'C,; Birds as Possible Carriers of the Virus of Equine Enceph- alomyelitis, Arch, Path, 25: 759, 1936 5 CHAPTER II THE MASSACHUSETTS OUTBREAK OF EQUINE ENCEPHALOMYELITIS EPIDEMIOLOGY In July, 1938 for the first known time, cquino encephalo- myelitis was found to infect horses in southeastern Massachusetts,In the course of about ton weeks, 269 deaths were reported. The geographical distribution of deaths in horses and cases in humans is given in Map I, The disease made its first appearance in the basin of the Taunton River which drains through nearby Rhode Island, The outbreak spread in a north- easterly direction into the upper parts of the Taunton River drainage area. There were relatively few cases to the south and southeast and none on Cape Cod, which is separated from this area by Buzzards Bay and Cape Cod Canal, The outbreak spread northward to metropolitan Boston and isolated cases oc- curred as far north as Maine and as far west as Worcester, About 70% of the cases among horses in Massachusetts occurred in a thirty mile square, ex- tending from the mouth of the Taunton River in the south to Boston on the north, and from the boundary of Rhode Island, eastward to the coast of Mass achusotts, Rhode Island to the west reported 55, and Connecticut 29 cases. During the summer and early autumn, rainfall in southeastern Massachusetts and Rhode Island was unusually heavy, and as a result mos- quitoes were unusually prevalent in these areas. The prevailing winds in that region arc from the southwest; and since the outbreak spread in a northeasterly direction, it is suggested that infectious mosquitoes may have been carried by those winds and may have quickened the spread of the epidemic. Horses which v/orc apparently well wore moved from one country fair to another; in one such instance a horse was moved thirty miles from an area where the disease was prevalent to the northeast to a town near the coast. Although without symptoms when moved, the horse became ill on the following day and a diagnosis of equine encephalomyelitis was proved by the isolation of the virus from its brain. Thus, the movement of in- fectious horses may have been a factor in the spread of the disease,Dur- ing the outbreak, Fothcrgill and Dingle isolated the eastern type of vi- rus from the brains of a pigeon that died in southeastern Massachusetts, and Tyzzer, Sellards and Bennett isolated the same virus from the brains of ring-necked pheasants from Connecticut, These findings suggested that birds may be the reservoirs of the disease and were factors in its spread. Almost simultaneously, in the same area, a now type of enceph- alitis appeared among children. This outbreak of encephalitis among hu- mans was the first known infection of man with the eastern variety of e- quine- encephalomyelitis virus. The prevalence of the disease among hors- es and humans is given in Figure I, The median date of reported deaths among horses occurred during the week ending August twenty-seventh, or two weeks in advance of the median date of onset for cases in Appar- ently, the peak of the outbreak among horses preceded that1 of the outbreak among humans by an interval of over two weeks. Although the prevalence of 6 DISTRIBUTION Of EQUINE ENCEPHALOMYELITIS MASSACHUSETTS 1938, L F G E N D A CASE S ! N H U MANS O DEATHS IN H ORSES MAP I 7 the disease was much greater among horses than among humans, the rise and fall of the outbreak in these groups was the same.The outbreak began slow- ly without increase for four weeks; and then rapidly reached its peak in two weeks. Remaining at this peak level for about a week, the outbreak subsided more slowly than it began. The last case was reported late in October, sixteen weeks after the beginning of the outbreak. There wero no multiple cases among families, and multiple cases on the seme farm or in the same stable were rare among horses,These field observations confirmed experimental evidence that the disease is not trans- mitted by contact. ANALYSIS OF CASES IN MAN In 1938, Foemstcr reported on the outbreak. Additional data has been collected since this report was made. Forty-four suspected cases of equine encephalomyelitis have been investi- gated, From nine of the patients Fothcrgill ct al and Webster and Wright isolated the eastern virus. The same workers established the diagnosis of equine encephalomyelitis in ten other instances by finding neutraliz- ing antibodies for the same virus in the blood of these patients. Eight other eases were diagnosed on the basis of pathognomonic brain lesions at autopsy. Those autopsies were performed by Branch, Farbor and Alexan- der, A diagnosis of equine encephalomyelitis was considered justified in seven additional patients because of the characteristic clinical findings. These eases were fatal and were not autopsied; blood specimens for neu- tralization tests were not obtained. Ten other cases wore suspected of being due to the eastern variety virus, but investigation revealed that a diagnosis of equine encephalomyelitis was unwarranted. In all, there wore thirty-four patients in whom the diagnosis of infection with the eas- tern variety virus was accepted by the Massachusetts Department of Public Health, 1958 MOSQUITO SURVEY As soon ns the true nature of the equine encephalo- myelitis outbreak was realized, the Massachusetts Department of Public Health, with the assistance of the United States Public Health Service, un- dertook the organization of a mosquito survey. A small group of college students, who had had biological training, was employed for this Survey, Collections were begun late in September and were limited to those towns in southeastern Massachusetts where eases of equine encephalomyelitis were most numerous. On September 21, a severe hurricane swept over New England; the .storm lasted several hours and the wind damage was great. As a result of this storm, many mosquitoes were destroyed; adults were killed by heavy wind and larvae succumbed due to the heavy rain and disturbance of the wa- ter surface. The collections of specimens which were made subsequent to the hurricane are, therefore, not representative of the normal prevalence of these insects. The vast majority of the specimens collected in October were Culex and Anopheles, Only a few Acdos specimens wore collected,These findings do not represent the actual distribution of mosquitoes during the continuation of the outbreak, which reached its peak about the middle of August, OBJECTIVES OF THE 1959 SURVEY Since information concerning the distribu- tion and prevalence of the presumptive mosquito vectors was required be- fore ah attempt to control them could be made, it was decided to make an- other effort to collect the data during the ensuing "summer, A study of the history of equine encephalomyelitis reveals that the disease often recurs in the' same region in succeeding years. Therefore, during the early months 8 MASSACHUSETTS-1938 ' ’ SEASONAL INCIDENCE OF EQUINE ENCEPHALOMYELITIS LEGEND ' O O H U M A N CASES (V o c E AT HS IN HORSES 9 of 1939, the Massachusetts Department of Public Health began to make plans for a State-wide mosquito survey. The objectives were to ascertain the true status of mosquitoes as vectors, to find naturally infected mosquitoes if the disease recurred, and to'collect data on the distribution and preva- lence of the presumptive vector. This information would, then, be applic- able to the control of the disease if it were to recur. As a survey of this type would moire collections of oil species of mosquitoes, it was decided to utilize this opportunity to collect data on the distribution and prevalence of all mosquitoes; to make a study of the ecological and entomological factors which influenced the breeding of the various species, and to record this information in such a way that it could be used' by the State Reclamation Board, which is in charge of all mosquito control work in Massachusetts• In this way the objectives of the Mosquito Survey wore enlarged to encompass the collection of all data that rcoul'd bo obtained concerning mosquitoes which wore prevalent in Massachusetts, and to determine the relationship of mosquitoes to those diseases which are transmitted by these insects in Massachusetts; namely, equine encephalomye- litis and malaria. BIBLIOGRAPHY Farber, S,; Hill, Allen M,; M* L,) Dingle, J, K,j Equine Enceph- alomyelitis in Infants and Children; Submitted to J, Am* Med, Assn, 1939 Feemster, R* F,; Outbreak of Encephalomyelitis in Man due to the Eastern Virus of Equine Encephalomyelitis, Am, J, Pub, Health 28: 1403-1410, 1938 Fothergill, L, D,; Dingle, J, H,; Farber, S.; Connerly, M, L,; Human Encephalitis Caused by Virus of Eastern Variety of Equine Encephalomyelitis, N. E. J* Med, 219: 411. 1938 Webster, L. T,; Wright, F, H,; Recovery of Eastern Equine Encephalomyelitis Virus from Brain Tissue of Human Cases of Encephalitis in Massachusetts. Sc, 88: 505-306, 1958 Wesselhoeft, C,; Smith, E, C,; Branch, C, F,; Human Encephalitis, J, /an, Med. Assn. Ill: 1735-1741, 1938 10 CHAPTER III OTHER MOSQUIT0-BORNE DISEASES Equine encephalomyelitis and malaria are the two most im- portant mosquito-borne diseases in Massachusetts. However, there are certain other diseases, some of which are and some of which are sus- pected of being mosquito-borne and which either occur or may occur in this state. These diseases have been placed into three groups in Table II. All of them have occurred in the United States and are, therefore, con- sidered as possible invaders of Massachusetts. TABLE II Disease with Proved raid Suspected Mosquito Transmission in the United States Proved Mosquito Transmission Laboratory Mosquito Transmission Suspected Mosquito Transmission Malaria * Equine * Encephalomyelitis Poliomyelitis * * Yellow Fever ** Lymphocytic * Choriomeningitis St, Louis , Encephalitis Dengue • Pilariasis • • • * Currently present in Massachusetts ** Formerly ” 11 ” • Hot known to be indigenous in Massachusetts Diseases With Proved Mosquito Transmission MALARIA Malaria is the most widely distributed mosquito-borne disease in the world. It has caused more suffering and death than any other single insect-borne disease. This disease has caused the downfall of groat empires, the abandonment of cities and fertile areas, and today is still a great problem especially in tropical and sub-tropical coun- tries , 11 In Massachusetts malaria has existed from early colonial times. Although the reports of the disease prior to the twentieth century are not wholly reliable, it is apparent that there has been at least three epidemic waves of malaria in Hassachusetts, The first epidemic in Massachusetts took place at the close of the eighteenth century and existed in the western portions of both Massachusetts and Connecticut along the Housatonic River Basin, The second epidemic of malaria appeared in Connecticut in 1830 and spread to western Massachusetts where the disease persisted until about 1870. The third epidemic of malaria began in Now Haven in about 1850 and con- tinued to spread northward reaching Springfield in 1870, From there the disease spread in a northerly direction up the Housatonic and Connecticut Rivers, This last epidemic wave continued to harass the state until the end of the first decade of the twentieth century. Mortality Statistics Deaths from malaria were made reportable as early as 1842, At first those wore reported as intermittent fever and remit- tent fever, from 1855 to 1900 the terminology of this disease was changed to ague end remittent fever, from 1901 to 1911 to intermittent fever and malarial cachexia, and finally, from 1912 to date the disease was re- ported as malaria. A study of the reported deaths reveals that there have been several peaks during the past one hundred years. The first peak was reached in 1864 and was associated with an importation of the disease in Union soldiers who returned from the Civil War, A second and much larger increase in deaths due to malaria began to manifest itself in 1880 and continued until 1898 when the deaths began to decrease again. This second wave of malaria, as recorded in these reports, was caused by two factors. The first was an epidemic of malaria in Massachusetts which has, already been discussed. This outbreak persisted for many years and did not completely recede until the end of the first decade of the twentieth century. The disease was associated with an outbreak spread- ing northward from Connecticut and with the settlement in Massachusetts of immigrants from countries in southern Europe where malaria had a high index. The effect of the Spanish American War on this disease is seen in the peak of 1898; during this year many soldiers returned to Mass- achusetts, after contracting the disease in Florida and Cuba, VfiLth the turn of the twenteith century malaria deaths began to decrease rapidly and reached a new low in the late twenties. Deaths from malaria average 1,Q% during the last ton years. This indicates a case fatality of 8,9% on a basis of the reported cases over the same period. Morbidity Statistics It was not until 1914, however, that malaria it- self was made reportable, when the State Department of Public Health de- clared it to be a disease dangerous to the public health. At this time malaria was endemic in several places within Massachusetts. From the geographical distribution of these cases it is apparent that there wore several outbreaks of the disease within the past twenty-five years. 12 In 1915, the first year for which tho figures arc complete, the reported incidence of malaria was the greatest. Since then the disease has a continued decreasing geometric trend and has reached an extremely low level in the past five years. Malaria was prevalent in Boston from 1915 to 1928, However, most of these cases were in sail- ors who had acquired the infection in tho tropics and were hospitalized in this city. Some of tho cases, however, were definitely connected with a new sower project where Italian labor was employed. The high incidence cf malaria in Chelsea from 1920 to 1935 is explained by the fact, that tho United States Marine Hospital is located hero and it re- ceived many sailors from foreign countries. The epidemic prevalence of 1918 in Ayer was due to tho presence of large numbers of troops at Camp Devens, some of whom werc from the south. In all there are three areas in Massachusetts where malaria has existed within the past twenty-five years. In each instance the disease has ceased to exist in the area more than ten years ago. These three places are: (1) The Charles River Drainage Area, where the disease was prevalent from 1915 to 1921, Here the disease apparently occurred first in Natick and Newton and spread to the neighboring cor.munities of Ded- ham, Framingham and Wellesley. The town of Dedham has a large Italian colony; and this is also true cf Nil ford in the upper part of the Charles River where malaria was prevalent from 1919 to 1924, It is important to note that malaria was not made reportable until 1914 and, consequently, there is no data on its incidence in this area prior to that year. Ol- der residents of this Charles River Basin state that malaria was quite common in their childhood during the first decade cf the twentieth cen- tury, It is not unlikely that it nay have been a hangover from the ep- idemic wave of the last quarter cf the nineteenth century. Unfortunately, there were many more cases of malaria in this region than were reported. (2) Tho second region where malaria seems to have been endemic from 1915 to 1921 is tho Blackstono River Basin, in particular the towns of Uxbridge, Douglas and Northbridge, (5) The third endemic region can bo roughly described as the Taunton River Basin, Hero malaria persisted from 1915 to 1922. The sane etiological factors were responsible for disease in these regions, as in tho Charles River Area, Malaria Acquired in Massachusetts Tho Massachusetts cases can be di- vided into two major groups, intra-state infections and out-of-state infections. An analysis of the cases reported during the ten years 1930 to 1939 inclusive reveals that the vast majority of the cases are out- of-state infections. These are principally among immigrants who acquired the infections prior to their arrival in Massachusetts, travelers who became infected during their sojurn outside of the state, and among sail- ors who acquired the disease in the tropics and sub-tropics. The second groups of cases consisted of those who acquired their infection within the boundaries of Massachusetts, These native infections 13 are composed of three categories of patients. The first, and largest, consists of therapeutic infections among patients in mental disease hospitals; second, and smallest, is the group which received accidental infections by the medium of transfusion from a person who was an unsus- pected carrier of the malaria plasmodium in his blood stream; third, and most important, were the naturally acquired infections, which presumably resulted from the bite of infectious mosquitoes. "Within the ten year period studied, 1930-1939, there were only eleven instances where nat- ural infection within Massachusetts \vas probable. These cases were scat- tered throughout the Commonwealth and there is no evidence to suggest that there was any connection between them. In several instances, namely, two children who acquired the infection during 1938, there were malaria cases in the same or a neighboring household. However, the source of the infection in the other nine cases has not boon established. YELLOW FEVED Yellow fever is transmitted principally by Andes aegypti. Ex- perimental ly,. twenty-one other species of mosquitoes, Simmons, have been demonstrated to transmit this disease. However, neither the natural vector nor the experimental vectors arc indigenous to Massachusetts, In colonial times yellow fever appeared in New England. It was brought to port cities by sailing vessels which came from areas in the tropics and sub-tropics where yellow fever was endemic. The mosquito, Aedes aegypti; was able to survive on board these ships, breeding in water casks. Un- der favorable meteorological conditions and a temperature of over 72 F Aedes aegypti were able to survive and brood, and transmit the virus in northern climates until the arrival of colder weather. In this way, yel- low fever appeared characteristically in the summer end disappeared early in autumn. The outbreaks were limited to the vicinity of the seaports to which the vector was brought by the vessels. As Aedes aegypti is un- able to survive through the severe winters of the Uni tod States, yellow fever did not reappear on subsequent years unless it was reintroduced in- to the seme region. Ye] low fever may reappear in Massachusetts only if infcqtod Aodos aegynti are imported, if those mosquitoes breed in large enou0n numbers to bo temporarily established, and if the infected mos- quitoes bite people, who, in turn, infect Aedcs aegypti. However, the importation of yellow fever is highly improbable, not only because of the lack of brooding places on modern steamships, but chiefly because of the efforts of the United States Public Health Service, which quarantines all vessc2s and airplanes which come from areas where the disease in en- demic, or telcos such measures as to ensure the destruction of Aedes aegypti on board ships-or planes. DENGUE Dengue has never been known to exist in Massachusetts, although it has spread in epidemic waves through several of the southern states. It is transmitted by Aedes aegypti and Aedcs albopictus, both of which arc tropical or sub-tropical mosquitoes. As with yellow fever, the mosquito does not become capable of transmitting the virus until after an extrinsic period of incubation. The vector remains infectious for life and is, apparently, not injured by the infecting agent. Dengue, like yellow fever, can occur in epidemics only whore 14 there is a certain numerical relationship between the vector, the num- ber of cases and the number of susccptibles in the community. This disease may appear in Massachusetts under the sane conditions as yel- low fever. To date there is no record of its existence in Massachusetts, but due to its proximity it seems that, statistically, the chances of its introduction into the state arc greater than that of yellow fever. FILARIASIS Filariasis, due to Wuchoria bancrofti, is transmitted, prin- cipally, by Culex fatigans and Aedos variegatus. In all twenty-nine species of the genera Culex, Acdes, Mansonia and Anopheles have been demonstrated to transmit’the disease experimentally. This disease is# in the main, restricted to tropical and sub-tropical regions. However, indigenous cases have occurred in South Carolina. Since most infections do not present any clinical manifestation, the prevalence of the disease is difficult to estimate. The disease has not shown any evidence of extending to neighboring areas, and the chance of this disease reaching Massachusetts is very small. Diseases in which Mesquite Transmission has been Demonstrated EQUDIE ENCEPHALOMYELITIS Equine encephalomyelitis has been discussed in great detail,. The laboratory demonstration of mosquito transmission is confirmed by epidemiological observations. To date, naturally infected mosquitoes have not been found. However, it was net until 1931 and 1938 that mos- quitoes naturally infected with yellow fever were collected, years after the mosquito transmission of this disease was demonstrated by Reed, The collection of mosquitoes naturally infected with equine encephalomyelitis may not be accomplished for many years. LYMPHOCYTIC CHORIOMENINGITIS Lynphocytic choriomeningitis, a newly recognized virus disease, has been experimentally transmitted with Aedos aegypti by Coggcshall, The disease was first described by YTallgren in 1925, The virus was is- olated by Armstrong and Lillie in 1934, The disease infects all ages and both sexes, Blackfan describes it as a seasonal disease with a majority of the cases occurring during winter and early spring. Ex- periments .have demonstrated that although infection may be acquired through an abraded skin, that it is not spread by direct contact. Eval- uation of the above experimental mosquito transmission is not yet pos- sible, If this disease has a mosquito vector, it must be some mosquito other than nodes aegypti, as it has occurred in regions where this species is not found. The possibility of other arthropodal vectors must be con- sidered. To date there is no report of the isolation of the virus of lymphocytic choriomeningitis from man in Massachusetts. Several clin- ical diagnoses have been made, but none have been reported as confirmed by serological examination. Laboratory workers who have handled the disease, have developed immunity as demonstrated by mouse protection tests. In investigations cf routine sera from diagnostic laboratories, several positive protection tests have been obtained. Naturally infected 15 nice hc.vo been demonstrated in Massachusetts. Epidcnics of the di- sease have occurred in Lcs Angelos, V/hothor or not it nay occur in Massachusetts in cpidonic fom is inpossiblo to foretell. The nos- quito transnission of lynphocytio choriomeningitis needs confirmation before it can be accepted. If Blackfan’s observation of the peak in- cidence of the disease in winter end early spring is confirmed, then some other arthropodal vector nay bo res’ponsible for its spread. The transnission of this disease by Demacontor andersoni has been reported by Shaughnossy and Milzor, They wore able to infect guinea pigs by the bite of nymphs which had been infected in the larval stage. Feces from infected tibks, when rubbed into the abraded skin of guinea pigs, likewise transmitted the disease. Diseases with Suspected Mosquito Transnission POLIOMYELITIS Poliomyelitis has been suspected of insect- transmission be- cause of certain epidemiological features. Several arthropods as body lice. Podicuius vestinonti, head lice. Podicuius capitis, bedbugs, Cimcx lectularis, fleas, flies, Calliphora vomitoria and LIusca donestica have yielded negative results in attempts to isolate the virus from their bodies. Attempts to transmit poliomyelitis by bites of insects have been uniformly negative. IToguchi and Kudo attempted to transmit poliomyelitis to liacacus monkeys by Culex pipiens. ■ They fed young ]a rvao with the virus in the polluted water in which they were growing and allowed the emerged adults to bite monkeys. Those experiments wore negative. Attempts to transmit the disease by the -bite of mosquitoes who had formerly fed on infected monkeys were likewise negative in experiments conducted by these inves- tigators. Flcxncr and Clark were unable to demonstrate the survival of poliomyelitis virus in Culex pipiens, Aedes sollicitans and Aedos cantator after they had fed upon infected monkeysT Simmons, Xclser and Cornell unsuccessfully attempted tc transmit poliomyelitis to monkeys by Aedes iQgypti. * . . . The mosquito transnission of poliomyelitis is highly improbable because of the very nature of the disease. The virus has not been dem- onstrated to be present in the blood of human beings at any stage of the disease. The inconstant presence of even snail amounts of virus in the blood of experimentally infected monkeys, the largo amount of virus re- quired to produce even- inconstant infections by the intravenous route, and the contemplation of the relatively small amount of blood which a mosquito could transfer even after an interrupted meal exclude the theory of mosquito transnission. Although the majority of cases of clinical poliomyelitis ap- pear in the summer, the disease continues throughout the year. There- fore, the mosquito, which, except for a few lethargic adults, is hiber- nating, cannot be classified as the vector; this fact is confirmed by winter epidemics of poliomyelitis. If poliomyelitis is a nosquito-borno disease, the vector must be world wide in distribution, as the disease has occurred on all continents. To our knowledge, there is no insect- 16 borne disease which has such a universal distribution. Our observa- tions here in Massachusetts indicate that there is no correlation be- tween the prevalence of mosquitoes and the existence of the disease. 193b was a year when mosquitoes were unusually prevalent, yet polio- myelitis remained at a very low subcpidenic level of only 18 cases, as compared with the tricentral moan of 168 for the past nine years. In 1939, mosquitoes were much less prevalent than usual, nevertheless, the number of poliomyelitis cases increased to 76, four tines as groat as in 1938. If this disease were mosquito-borne, the opposite phenomenon would be expected. In conclusion, it nay be srid that all epidemiolo- gical and experimental investigation indicates that poliomyelitis is not transmitted by mosquitoes. GT. LOUIS LliCERLALITlS St. Louis encephalitis is a specific virus disease which can be serologically distinguished from other enccphalitides. This disease has recurred for several years in the middle and far western states. It is typically a late summer and early autumn disease. In 1933, the famous St. Louis outbreak started early in August, reached a peak early in September, and ended with the onset of cold weather in October, I.let- eorological conditions were unusual at this time in St, Louis, The city experienced less rain in that summer than in any year since 1837, Many open drains containing stagnant water became breeding places of mosquitoes. Because of the abundance of these insects during the outbreak, investi- gations wore undertaken to determine if mosquitoes can transmit the di- sease. Simmons and Cornell fed Andes aegypti on patients admitted to the hospitals of St. Louis, and thereafter permitted the mosquitoes to bite experimental animals. All these experiments wore negative. Leake, Musson and Chope carried cut more extensive experiments with Culox pipiens, Anopheles quadrimacu1atus and Aedcs aegypti. The results were all neg- ative, -Leake concludes; "In spite of entire failure under a wide variety of experimental conditions, we cannot say that the possibility of trans- mission of encephalitis by mosquitoes in nature is finally disproved," Later, hobstor. Clew and Bauer demonstrated the survival of this virus for life in nnopholes q.uadrimaculatus, Mitamura, Yamada ot al wore able to transmit both the St, Louis encephalitis and the Japanese B enceph- alitis by Culex pipiens var. gallons. This work, however, needs con- firmation before it can bo accepted, humsden has reviewed the epidem- iology of the St. Louis outbreak and concluded that Culox pipiens might have been responsible for the transmission of the disease. Reporting upon an outbreak of St. Louis encephalitis in California, ITowitt remarks that mosquitoes wore abundant in the regions where the disease was pre- valent. To*date St, Louis encephalitis has net been reported in Mass- achusetts, However, its recognition in such widely separated areas as Indiana and California indicates that the disease has involved hitherto unsuspected areas. The problem of mosquito transmission of St. Louis encephalitis remains unsolved. The negative experiments cited above are inconclusive evidence, as the insects wore, of necessity, fed upon patients who were admitted to hospitals and, therefore, well advended in the course of the disease. If the virus wore present in the circulating bleed only during 17 the early stages of the disease, the experiments were, per force, neg- ative, Further investigation must determine the role of the mosquito in this disease. Its seasonal distribution end the epidemiological ob- servation indicate that St, Louis encephalitis may be mesquito-borno. BIBLIOGRAPHY MALARIA Holmes, Oliver Wendell; Indigenous Intermittent Fever in New England Boylston Prize Dissertations of 1836 and 1837. Chas. C. Little and James Brown, Boston, Adams, J. F. Alleyne; Intermittent Fever in-Massachusetts. Annual Report of the State Board of Health, Lunacy and Charity; Supplement Public Health 1880; pages 45-108. Chapin, C, V,; The Origin end Progress of the Malarial Fever Now Pre- valent in Mow England, Fiske Fund Prize Dissertation, No, XXXII. 1884 Cook, Chas. H.; A Study of Malarial Fever in Eastern Massachusetts, P per read at Annual Meeting of Mass. Med, Society, June 11, 1889 Smith, Theobald; The Sources, Favoring Conditions end Prophylaxis of Mal- aria in Temperate Climates, with Special Reference to Massachusetts, Boston Med, & Surg, J, 145; 57, 87, 115, 139, 1903 Quinn, Hilton J.; Malaria in New Eraland; Boston Mod, & Surg. J. 194 244-247. 1926 YELLOW FEVER Simmons, J. S.; Insects ns Vectors of Virus Diseases. Symposium on Virus end Rickettsial Diseases, pages 118-175. Harvard Press, Cambridge, Mass, 1940 • • • ■ Carter, H. R,; The Early History of Yellow Fever. Williams & Wilkins Co, Baltimore, Md, 1931 Russell, Frederick F.; The Epidemiology of Yellow Fever. Symposium on Virus and Rickettsial Diseases, pages 737-766, Harvard Press, Cambridge, Mass, 1940 Boeuwkes, Henryj Hayne, T. B.; An Experimental Demonstration of the In- fcctivity with Yellow Fever of Aodes aegypti captured in an African town. Transactions of the Royal See, of Trop. Hod, & Hyg. 25: 107-110, 1931 Hannon, R. C. S.; Whitman, L.j Franca, M,; Yellow Fever in Jungle Mos- quitoes. Sc, 88: 110-111. 1938 18 Gordon, John E.; The Preparation and Use of Yellow Fever Vaccine. Sym- posium on Virus raid Rickettsial Diseases pages 767-788, Harvard Press, Cambridge, Mass, 1940 .Whitman, L.j Failure of Aedos aegypti to Trcnsnit Yellow Fever Cultured Virus, (17D), Am, J. Trop, Med, IS; 19. 1939 DENGUE Simmons, J, S.; Dengue Fever, Am, J, Trop. Mod, XI; 77-108, 1931 Simmons, J, S.j Transmission of Dengue Fever by Aedes albopictus, Skuzc Philippine J. of Sc, 41; 215-231, 1930 FILARIASIS Dunham, C-, C,; Control of Insect-borne Diseases. Military Preventive Medicine, Amy Med, Bulletin, No. 23, Med. Field Service School, Cc.r lisle Barracks, Penn, 1938 Simmons, J. S,; Insects as Vectors of Virus Diseases. Symposium on Virus and Rickettsial Diseases, pages 118-175, Harvard Press, Cambridge, Mass, 1940 LYMPHOCYTIC CH0R1OMENING1TIS Coggeshall, L. T.; The Transmission of Lymphocytic Choriomeningitis by Mosquitoes, Sc. 89; 515-516. 1939 Wallgron, A.; Une ncuvello naiadio infoctieuse du systene nerveux central? ‘(Meningito asoptique aigue) Acta Paodiat., 1924-1925, 4: 158. Armstrong, C.j Lillie, R, D.j Experimental Lymphocytic Choriomeningitis. Public Health Rep., U. S. P. H. S., 492; 1019.' 1934 Blackfan, Kenneth Dj Lymphocytic Choriomeningitis, Symposium on Virus end Rickettsial Diseases, pages 684-700. Harvard Press, Cambridge, Mass, 1940 Armstrong, C.j wooloy, J. G.j Benign Lymphocytic Choriomeningitis. J. Am. Med. Assn. 109; 410, 1937 Shaughnessy, H. J.; Llilzcr, A.j Experimental Infection of Dermancentor andersoni Stiles with Virus of Lymphocytic Choriomeningitis, Am. J. Pub, Health 29, 1103. 1939 19 POLIOMYELITIS Howard, C. W.; Clark, P. F.; Experiments on Insect Transmission of the Virus of Poliomyelitis. J. Exp. Med, 16; 850, 1912 Kling, Patterson and Wernstedt; Investigations on Epidemic Infantile Par- alysis. Report ... to the XV International Congress on Hygiene and Demo- graphy, Washington, 1912. State Medical Institute of Sweden. Noguchi, H.j Kudo, R.; The Relation cf Mosquitoes end Flies to the Epidem- iology of Acute Poliomyelitis. J. Exp. Med, 26; 49, 1917 Flexner, S,; Clark, P. F.; Contamination of the Fly with Poliomyelitis Virus, J. Am. Med, Assn. 56: 1717. 1911 Simmons, J. S,; Kelser, R. A.; Cornell, V. H.; Attempts to Transmit the Virus of Acute /interior Poliomyelitis through Aedos aegypti. Proc. Soc. Exp. Biol. & Mod. 31; 496. 1934 Poliomyelitis. A survey made possible by a grant from the International Committee for the Study of Infantile Paralysis organized by Jeremiah Milbank. The "Williams and Wilkins Co., Baltimore, Lid, 1932 Aycock, W. Lloyd; The Epidemiology of Poliomyelitis. Symposium on Virus and Rickettsial Diseases, pages 555-580. Harvard Press, Cambridge, Mass, 1940 3T. LOUIS ENCEPHALITIS Epider.iic Encephalitis, Third Report by the Matheson Commissi on, Col- umbia University Press. 1939 Leake, J, P.j Musson, E. K.j Chopc, H, D.; Epidemiology of Epidemic Encephalitis, St, Louis typo. J. Am. Mod. Assn. 103: 728. 1934 Simmons. J. S.j Cornell, V. H,; Experimental Attempt to Transmit St, Louis Epidemic Encephalitis from Patients to Animals through Aedos aegypti. Unpublished Report, The Amy Medical School, Washington, D, C, 1933 Webster, L. T.j Clow, A. U,; Bauer, J, H.; Experimental studios in enceph- alitis, III Survival of Encephalitis (St, Louis type) in Anopheles quadrinacu1atus. J, Exp. Med. 61; 479, 1935 llitamura, T. and Yonada, S. et al; Uber don Infektionsnodus der cpidcm- ischen Enzephalitis, Epcrinentelle Untersuchungon uber ihre Ansteckung . durch Mucken. Tr, Japan Path. Soc. 27: 573, 1937 Howitt, B. F.j Viruses of Equine and of St. Louis Encephalitis in Relation- ship to Human Infections in California 1937-1938, Am. J. Pub. Health 29; 1085-1097. 1939 ' 20 CHAPTER IV THE CONTROL OF MOSQUITO-BORNE DISEASES Tho control of any mosquito-borne disease is based on one or more of the following procedures: I Control of the mosquito vector II Protection of man and animal from the bite of infected moaquitocs III Immunization of susccptiblos IY Removal of sources of infection of mosquito vectors by a. Isolation of cases b* Treatment of carriers V Prevention of entry of the mosquito vector and possible sources of infection into areas as yet unaffected by the disease All these methods are not applicable to every mosquito-borne disease. The diseases under discussion arc listed in Table III with a notation on the application of the various control methods. I Mosquito Control Certain conditions are necessary before a mosquito- borne disease can become epidemic or roach a high endemic index. One of these conditions is tho existence of a certain numerical relationship between the hosts, vectors arid susccptibles. lYhcn this numerical relation- ship is upset by a reduction of tho number of vectors, the disease ceases to bo epidemic and rapidly declines either arithmetically or geometrically, depending upon tho interrelation of many related factors. It becomes apparent that a moderate reduction in the number of mosquitoes below tho critical level will markedly reduce the prevalence of the disease in an area where there are many immunes, but in a region with many susccptibles, the reduction below the critical level must be much greater. This con- cept was developed by Ross'who applied it to malaria. Carter and Gorgas applied it to yellow fever. The bionomics of mosquitoes arc such that control measures must be' designed to eliminate or control the larvae or the adults. The measures which are most effective in any area depend upon the local factors and upon the genus and species of mosquitoes concerned. It is impractical and uneconomical to attempt to control all mosquitoes. The control measures must bo directed against that species which it is desired to reduce below tho critical level. Therefore, in order to insure effective control mea- sures, it is important to understand the bionomics, breeding,habits, and seasonal and geographical distribution of the species that are concerned with the transmission of the disease. Since local circumstances vary, it is necessary that a mosquito survey be made before control measures are introduced into a new area for the purpose of controlling mosquito- borne disease. Even in controlling mosquitoes as a nuisance, it is ne- cessary to determine their bionomics before an economical and’bfficicnt nuisance control can be expected. Mosquito control has been effective in malaria and yellow fever. 21 There has been considerable less experience in the effectiveness of this method in dengue, but since the principal vector of this disease is the same as for yellow fever, there is every reason to believe that mosquito control will prove just as effective. In filariasis, this method has also proved to be effective where it can be applied. To date, there has been no notable effort to control the vectors of equine encephalomyelitis. Theoretically, this method should be effective; but the natural vector of this disease has not yot been determined, and epidemiological and en- tomological investigations are needed before this method can bo applied. The'collection of this data is the primary objective of this mosquito sur- vey. TABLE III APPLICATION OF CONTROL METHODS TO MOSQUITO-BORNE DISEASES DISEASE Methods of Control* I II III IV V a b Malaria XXX XX 0 XX XX . 0 Yellow Fever XXX XX XX XX 0 XXX Dengue XXX XX 0 0 0 XX Filariasis XXX XX 0 0 0 Ox Equine )llorses X XX XXX Ox 0 0 Ence pha1omyelitis)Humans X XX Ox 0 0 0 ♦Methods I Mosquito Control II Protection from Mosquito Bites III Immunization of suscoptiblos IV Removal of sources of infection a. Isolation of cases b, Treatment of carrier V Prevention of entry into new area xxx Proved effective xx Only partially effective 3c Theoretically effective 0 Hot applicable II Protection from Mosquitoes Effective protection from the bites of mosquitoes can be accomplished only under very limited conditions. Screen- ing, and avoidance of unnecessary exposure, are the methods most effective. Spraying in houses, the application of mosquito repellants and swatting of adults are adjuvants. If this method wore to bo effective, animals and man would necessarily have to remain behind screens at all times. Since this is a physical impossibility, the protection against mosquito bites is only partial. This method is about equally applicable in all mosquito diseases; the differences arc dependent upon the habits of the adults of the species 22 concerned* III Immunization of Susceptibles Specific immunization has proved effec- tive in yellow feverl TE" is, however, not yet available to the public in all endemic areas. Although the vaccine is a live attenuated virus, there has been no resumption of virulence in over two million vaccinations performed in Brazil, Whitman demonstrated that mosquitoes which bit vaccinated per- sons did not infect monkeys on subsequent biting. Unfortunately, immunity is temporary and annual revaccination is required. In equine encephalomyelitis, a vaccine produced from formolized virus grown in chick embryos, has proved effective in the protection of hor- ses. As yet, this vaccine is not applicable to man, except for laboratory workers, due to severe reactions which have been encountered. Moreover, the risk of exposure to the disease has been so small that community immuniza- tion has not been indicated. Vaccination of horses must be repeated annually as immunity is temporary,, Mohler attributes the decreased incidence of this disease in 1939, in part, to the vaccination of horses. There is no specific immunization against the other mosquito-borne diseases. The prophylactic use of quinine in malaria is an attempt to destroy the plasmodium as soon as it is introduced into the blood stream. IV Removal of Sources of Infection is effective only to a limited extent. Cases of the disease, with the infecting agent in the circulatory blood, may act as foci of infection for vectors. Therefore, it is,theoretically, good preventive medicine to isolate those patients in mosquito proof quarters. Except for malaria and filariasis, which are, respectively, due to a protozoan and a helminth, the remainder of the mosquito-borne diseases arc duo to a virus which remains in the blood stream for a very short time, and which, in many instances, disappears from the blood stream soon after the disease mani- fests itself. Malarial gametocyto carriers arc the foci of outbreaks of the dis- ease in new areas, Filariasis' is often symptomlcss. As filaria may remain in the blood for prolonged periods, these carriers may act as sources of vec- tor infection. Malarial carriers may be eliminated by adequate treatment, but filarial carriers remain permanent, for there is no known effective drug therapy in this disease. V Prevention of Entry into New Areas This is a method which is applicable to all infectious diseases• The principals of isolation and quarantine are utilized in every community. In the case of certain diseases, especially those with a wide host selectivity, the prevention of the spread of a disease becomes more difficult. This feature is well illustrated in the case of yel- low fever. The disease was apparently controlled by the use of the usual methods and isolation and quarantine on a community-basis*- Suddenly, it be- came apparent that jungle yellow fever was due to the persistence of the dis- ease in other hosts and vectors. Equine encephalomyelitis has an even greater host selectivity. Its spread may be due to vectors or hosts. Since the hosts include animals and birds, the geographical limitation of this disease becomes a difficult problem. 23 Malaria and filariasis are usually spread by hosts who are not known to be infected. In modern civilization and rapid transportation, it is practically impossible to eliminate the travel of such individuals. Conclusion In summary it may be said that when control methods are de- pendent upon control of man, only limited success may be expected, as some individuals are uncooperative. The most effective method in the control of mosquito-borne dis- eases has been the reduction of vectors to below the critical level which will maintain the disease. BIBLIOGRAPHY Mohler, J, R.j Report on Infectious Equine Encephalomyelitis in the U, S, in 1939, United States Department of Agriculture, Bureau of Ani- mal Industry, Washington, D, C, 1940 Whitman, L.j Failure'of Aedes aegypti to Transmit Yellow Fever Cultured Virus, (17D), Am, J. Trop, Med. 19: 19, 1939 24 CHAPTER V ORGANIZATION The Mosquito Survey was organized as a separate activity of the Division of Communicable Diseases in the Massachusetts Department of Public Health. The director of the Division of Communicable Diseases v;as responsible to the Commissioner of Public Health for activities of the Survey, In direct charge was the technical director who was respon- sible for the administration of the Survey, the analysis of the find- ings and the compilation of the final report. Although it was an activity of the Department of Public Health, the Mosquito Survey was made possible through the cooperation of the .Work Projects Administration, Various federal, state and private organizations participated in the Survey’s activities. Exclusive of the technical di- rector and the entomologists, the personnel of the Survey were all 17ork Projects Administration employees. The Massachusetts Department of Agriculture, through the Divi- sion of Livestock Disease Control and the Massachusetts Reclamation Board, cooperated in the activities of the Mosquito Survey, The Massachusetts Reclamation Board, composed of members from the Department of Public Health and Agriculture, is in charge of mosquito control projects in the Commonwealth, This Board, through its vast knowledge of mosquitoes in Massachusetts, assisted in laying out the program of the Survey, Harvard University, through the Medical School and School of Public Health, gave active help. The Department of Preventive Medicine and Epidemiology, the Department of Bacteriology, and the Division of Biology assisted the Survey by furnishing quarters and some equipment. Members of the several faculties took part in the training course of the field personnel. STATE PERSONNEL The Survey itself was divided into two parts; the state employees, and the Y/ork Projects Administration employees. Of these, the state employees formed the smaller portion, consisting of the entomo- logical staff and several members of the Division of Communicable Diseases, who, although not actual members of the Survey, rendered valuable assist- ance during the months of organization. The organization chart on the following page, clarifies the exact status of the Survey personnel and of the various volunteer cooperating groups. The entomological staff was composed of a consultant entomolo- gist, chief entomologist, four entomologists and four assistant entomol- ogists, In addition to their taxonomic activity, the entomologists as- sisted in the training of the field personnel, made special collections in the field, aided in the supervision of technical details, revised the identification key, and made permanent collections of mosquito adults and larvae for research and teaching purposes. VfT C.AMg! *URCAN [ STAT F j FE. i SON S| MOSRlmTo! COMT ROvJ OTHER, j j V'<5TZTJF~!Yf sbs NAVY SJMMER CAMPS j M ET EOPOLlTAN DISTRICT COMMISSION MACS-DEC', or AGEiCU LTu'Et |0!v:c-on of :-!StARt CW.'TLJU LOCAL BOARDS CE MEALT H 551. I Arm y C- c c. 1 C Mv?S j STATE LosWTkJ LOCAL kV/AT E B. »0. 1 School: Toy i GiFL Scoots CONSULTING UNTOMOLCOiST ! j SP-E NTC MCtOft! ST | JR..ENTOMr>»_06t. MOEUUIT O COMTILff. — " ! 1 p-V ! s? ON OF I com m u Kit c» s*.e Disease MuSOUlTD SURVEY ORGANIZATION C M A R.T ■state DISTRICT Health OFF.cto-s jDF.r>' jN jpUEA RCKf!TAT I ST ICG 1 SUPtBV** I*ut- SUPfc.IV IJIMO j DRAFTSMvH RA'ilAN I STATISTICIAN JUNIOR. ST AT ST Cl A* I PUNCH-CA60 OPEB.COCV 2, SUNCM-CARD ORATORIES TECHNICAL Dl R.E.CTOE OF SUEvtY 1 Fig LD \Vo AREAS VPIRVISOC-S 4 j CREVFOUEMfcN 20 A?»ST FOREMEN 20 collectors M AP.V.AS.D UNivgn siTy M CPiCAl. SCM.OOL CUiEFaERK J FILE LfeR« O O ST'NT: CLt CV.S * CHECKING CL5RK \ SUMMARY CLER VC5 Z FQ^TiMf, SCMOClof PU5L1C HEAtTL! WORK- P RO ]ECT 5 j A DM I N 1ST P AT I OKI j P P. CJ E CT S U P E H. V I SCR- ) ADMINISTRATIVE | C Hi EE CLERK. I TIMEKEEPER. F’le clerk. 1 STENOQUAFMEftS H TYPISTS C MtSSENGgo j maintenance z 26 WORK PROJECTS ADkllJI STRATI ON FERSOITKEL The second portion of the per- sonnel was the Work Projects"Administration employees, with a project supervisor in charge. It comprised two sections, the office and the field personnel. Office Personnel Although nominally in charge of the project super- visor the office work was actually administered by the two chief clerks. This was especially true on occasions when the project supervisor found it necessary to be away from the central office on trips requiring an absence of more than one day. The office personnel was divided into four categories: 1, Administrativo This portion was in charge of one of the chief clerks, and consisted of a timekeeper, two stenographers, five typists, one file clerk and a messenger. Their duties were: first, the handling of the many Work Projects Administrate on details; second, corrcs pondcncc; third, filing and supervision of survey sheets; fourth, mailing of pamphlets and letters to volunteer collectors, and many other mis- cellaneous tasks. 2, Posting of Data This portion comprised one chief clerk, one file clerk, five posting clerks, one checking clerk and two summar- izing clerks, whose duties were to post the collection and identifica- tion data, arid after summarizing it, to code it in preparation for the punch card analysis. The number of the personnel in this group varied greatly and was enlarged to more than thirty during the final analysis of the data. 3, Supply The supply room was concerned with the prepara- tion of material used in the collection of specimens and in the prepara- tion and mimeographing of literature for use by the Survey, There were one chief laboratory assistant and four laboratory assistants in this group. 4, Specialists The fourth and final group of the office per- sonnel consisted of various specialists, A research worker was assigned to build up a bibliography on subjects of interest to the Survey, A draftsman, with a junior draftsman and two tracers, assisted the techni- cal director in the compilation of charts, tables and maps, A statisti- cal clerk, with a junior statistical clerk and two punch card operators, assisted in the punch card analysis. Field Personnel The state was divided into four approximately equal areas, one area supervisor being placed in charge of each. These areas, in turn, were further divided into districts of which there were twenty in the Commonwealth or an average of five districts per area. Each dis- trict consisted of several towns and was assigned a crew foreman. The number of towns included in these districts varied from six to twenty-six with an average of 17,6 towns-per district. In addition to the crew foreman, each district was assigned a field crow of one to six men, the average number being four. The actual number of men working in each district depended on the number of 27 towns in the district. An example is Franklin County which was incorpo- rated as District $16, comprising twenty-six towns. This district was in charge of a crew foreman and six crow members. The state was divided into districts and the districts were divided, originally, into four portions; each portion was to consist of a single day’s work, as the original plan of the Work Projects Administration was to work four days a week. Shortly after the project started, however, new Work Projects Administration regulations were enforced, changing the work schedule of the project to a five-day week program. The districts were, therefore, divided into five portions one portion to be covered each working day of the week. In this way, each district was covered completely once a week. Wherever possible, one man was to cover one town in one day. However, with the introduction of a five-day week, this plan had to bo modified. The field work was under the direction of the four area super- visors. Each of these was responsible for tho collection of data and specimens in his area. His work consisted of periodical visits to each district, during which he supervised the administration of the district, chocked workers in the field, left supplies for the coming week and picked up collections which wore made during the preceding week. He checked the district records, survey sheets, and volunteer W, P, A, collections. Once a week a conference was held at headquarters in Boston, Hero the supervisors recoivcd supplies for tho forthcoming week, were given instructions concerning problems which had'arisen, and loft collec- tions which they had obtained from each district. Each crcvv was under the direction of a crew foreman who owned an automobile which he used to contact local boards of health. Boy Scouts, Y,M,C,A. and other summer comps end schools. Whenever possible, he arranged his schedule so that he worked in the same towns in which his crew was collecting. He acted as contact man between the Mosquito Survey and such organizations as were to do volunteer collecting. Enlistment of volunteer collectors by public speeches and demonstrating was one of the more important duties. Supervising and checking the work of the crew formed a second important item in the foreman’s schedule. Ho checked the crew in and out in the morning and afternoon, gave them supplies at the beginning of the day and collected the specimens in the evening. All specimens were inspected for the presence of larvae or adults and for corrcqt labeling and filling of the vials. Survey sheets were chocked for completeness and accuracy. The foreman kept each crow member’s 'col- lections separate and turned these over to the supervisor with a 'report as to the number of collections made by each man, each day of the week. The third important duty of the crew foreman was keeping accurate and complete records. He made a copy of the survey sheet; the original was kept tnd filed at the district headquarters and the copy was sent to the central office in Boston, It was the foreman’s duty to see to it that each crew member sent in the required weekly reports and that he himself submitted summary reports for the work -of the crew each week. The assistant crew foreman was responsible in the absence of the crow foreman. Each assistant foreman owned and operated an auto- 28 mobile in- which he transported the crew. The assistant foreman travelled over a designated route and dropped off crew members at designated points, one in each town. Thereafter, he proceeded to the farthest and usually the largest town where he collected as did other members of the crew, with the exception that ho travelled from point to point in his auto- mobile . The chief duties of the crew members were the collection of adults and larvae and the establishment of collection points. Crew members met at' a designated point in each district before nine o’clock in the morning, • By nine o’clock the crew had received such supplies as it needed for collections that day, and then was transported to towns which were to be covered during the day’s work. One by one they were dropped off in different towns where they proceeded on foot between collection points. According to the W, P, A, regulations, the crew worked five six-hour days per week. There was a one hour lunch and rest period between twelve and one o’clock. On the return trip at the end of the day, the assistant foreman arranged his schedule so that he met the last crew member'at three o’clock. This was in accordance with W, P, A, regulations. The remainder of the trip was made on the worker’s time. In certain instances, some crew members were requested to visit summer camps in an effort ’to enroll volunteers. Such instructions were given by the supervisor or foreman. The project supervisor was responsible for the work of all the Work Projects Administration personnel. However, because of the technical nature of the work, it was often desirable to have the techni- cal director explain the particular task epneerned, to the worker, indi- vidually, On all such occasions, the supervisor and any other persons concerned, were called together and the situation was explained to the group. In this way, the project was able to accomplish more work in a shorter period of time, and, with the cooperation of the project super- visor, to circumvent many delays which would have otherwise intervened. In summary, the field personnel consisted of one project super- visor, who was also in charge of the Work Projects Administration office personnel, four area supervisors, twenty crew foremen and eighty-tv;o crew members. The total- field personnel numbered one hundred and seven. VOLUNTEER COLLECTIONS A substantial portion of the collections made during this Survey were obtained by volunteers. Approximately 10% of the total collections and about 50% of the adult collections were made by them. Volunteer collectors were enrolled systematically upon appli- cation blanks furnished by the Survey, The names and addresses were filed in the central office and each collector was given an identifying number. Upon receipt of an application, a letter was sent to the volun- teer collector informing him of his identification number and the source of supplies. The application blank contained information about the Survey, In addition to the letter, bulletins on mosquitoes and enceph- alitis and from time to .time a pamphlet entitled "Massachusetts Mosqui- toes" were sent to the volunteer collectors. In all, there were five of 29 these bulletins during the season. The enrollment of volunteer collectors was begun by the per- sonnel of the Division of Communicable Diseases of the Department of Public Health, Epidemiologists and District Health Officers contacted the three hundred and fifty-one local Boards of Health and arranged for visits by employees of the Mosquito Survey* At the same time, sam- ples of literature and supplies were left at each Board of Health* During the first few months of the.Survey, crew foremen in each district re-visited the Boards of Health, left additional supplies, and collected such specimens as had been obtained. Periodically, Boards of Health were visited throughout the continuation of the Survey, During the summer months, the best cooperation from volunteer collectors was obtained in summer camps, state institutions and federal institutions. Although summer camps were, as a rule, of comparatively short duration, valuable contributions were made by many of them. Boy Scout and Girl Scout Camps did excellent work. Several of the state hospitals and the Department of Mental Hygiene made valuable contributions. The United States Havy submitted collections throughout the season from several places along the coast line. The Brookline Board of Health, in charge of the Mosquito Con- trol Project of this town, made regular collections from the Survey from May through October and brought the specimens to the laboratory. The Cape Cod Mosquito Control Project was perhaps the largest contri- butor of volunteer specimens during the Survey, The supervisor and the entomologist of this project collected specimens for us and arranged for their workers to do likewise. In addition to the collections v/hich the Cape Cod Mosquito Control Project personnel itself made, the workers enrolled many volunteer collectors and submitted numerous specimens to us from Barnstable County. The State Reclamation Board personnel made numerous collections, especially during the earlier part of the season. The Nantucket Mosquito Control Project also assisted the Survey in making collections on the island of Nantucket, All the volunteer collecting carried out by organizations in the state other than those already mentioned above, was in direct charge of the personnel of the Survey, Supervisors and crew foremen mot with various intra-state groups, and gave lectures and field demon- strations, Approximately one-half of the time of the crew foreman was devoted entirely to the organization of volunteer collectors. Such specimens as were picked up by volunteers, were usually brought to a place designated by the local Board of Health, and then collected per- • iodically by a representative of the Mosquito Survey, New supplies for volunteer collectors were likewise left at these places, and were always in sufficient quantity to meet local demand. The collections made by the volunteers were particularly important in that they consisted principally of adult mosquitoes, whereas the collections made by the personnel of the Survey were, in the main, larvae. Moreover, one species, Psorophora ciliata, was collected only by volunteer collectors. Although the total number of collections made 30 by the volunteers was comparatively small, we feel that better results can be obtained in the future by organizing the Survey in the spring. During the months of September and October the Survey person- nel was able to visit teachers and various nature groups in some of the high schools throughout the state. The response from these groups was most heartening and resulted in an appreciable increase in the number of volunteer specimens submitted. It is our opinion that if the high schools are contacted early in the spring, the number of volunteer collections will nearly equal, if not exceed, the number submitted by the Survey personnel. In all, over 6000 collections were made by the volunteers. Unfortunately, during the summer there was a drought in Massachusetts, and as a result, mosquitoes were comparatively scarce. This was in marked contrast to the summer of 1933, when mosquitoes were unusually prevalent duo to the heavy summer rains. It is our feeling that had mos- quitoes been a real nuisance during the summer of the Survey, the re- sponse from volunteers would have been much greater* 31 CHAPTER VI COLLECTION OF SPECIMENS COLLECTION POINTS Most of the plans for the Mosquito Survey were drawn up during the early part of the spring of 1939. Since it was desirable to begin the Survey as soon as appropriations were made, it was necess- ary to have on hand sufficient material to enable the field workers to begin immediate mosquito collections. As it was our desire to make regular periodical collections at prescribed points throughout the Com- monwealth, such places as we thought would be permanent collection points had to be selected. A collection point was defined as an area 100 yards in radius, about some permanent landmark as a center. Such a collection point may have been in the woods, meadow, or at the edge of a large pond. In the last instance, the center which was chosen was a prominent, easily identi- fied landmark on the shore, and the collection point area extended 100 yards in either direction along the shore and 100 yards inland. Before field work was begun permanent collection points were selected by two methods, 1, Maps of Massachusetts, prepared by the U, S, Geological Survey, were obtained. On these maps, marshes, swamps, slow-moving streams, ponds and other large water bodies, which, according to the terrain, appeared to be suitable for mosquito breeding, were selected as collection points, 2, In certain portions of the Commonwealth, the Massachusetts Reclamation Board and its many affiliates wore carrying out mosquito control projects. Members of the Reclamation Board ?/ore able to spot on these Geological Survey maps, places where they knew mosquitoes were breeding. Thus, by two methods, we were able to select between ten and twenty collection points in almost every town in the Commonwealth, This made a total of from 3510 to 7020 collection points for the 351 towns and cities. At the completion of the training course, about the middle of June, the foremen returned to their districts and began the training of their personnel. During the-second week of training, many of the collec- tion points selected by us were visited by the crews and surveyed. There- after, new collection points were selected by actual field experience. For example: If a crew member found a good mosquito breeding place which was likely to remain permanent throughout the season, he made out a survey sheet for that point, relaying the information to his foreman, who in turn, passed it on to the area supervisor. The area supervisor, in the weekly conference at the Boston headquarters, submitted the new' collection point to the technical director and the entomological staff, who decided, on the basis of the accompanying specimens and survey sheet, whether or not the collection point was desirable. If so, it was approved. At the beginning of the Survey, each crew was supplied with a duplicate sot of maps of the towns in its district. These wore-maps which were compiled by the Massachusetts Geodetic Survey in 1936, They were printed on 8v x 11 inch paper and fitted easily into the crow members’ carrying kits. On each map were spotted the collection points as selected 32 before the field work started. New points were spotted as they were made. Area supervisors wore furnished with a book of these maps to which they transcribed all the approved collection points in their area. The area supervisorsf map books were brought to ‘the central office from time to time where the approved collection points were transcribed into a master map book of the. entire state. In order to obtain detailed information concerning each collec- tion point, a Survey of Collection Point Form was devised. It may be pertinent to mention at this point that this form and labels which wore • used by the field workers were approved by the Work Projects Administra- tion as being of such a character as would obtain the desired information with the least' possible likelihood of error. It was realized that with lay collectors such as we trained, forms, which were not too complicated, but which contained sufficient material readily adaptable to being trans- ferred to punch cards, had to bo developed. Accordingly, we devised a form which was simple to fill in, and contained the information which we desired to use in our punch card analysis. This Survey of Collection Point Form was made out in duplicate. The copy was sent to the Survey headquarters,where it was filed. 'These copies gave us a check on the number of collection points that were being"visited regularly in the various towns of the Commonwealth* Therefore, we were able to say in how many places collections were being made at any given tine. The original of the survey sheet remained with the crew foreman who was thus able to check the survey and at the same time enabled the continua- kj tion of collections at these points whenever a change of personnel occurred. For a detailed description of the Survey of Collection Point Form the reader is referred to tho bulletin, ’’Training Course for Field Personnel”, Survey of Collection Point A Survey of a collection point consisted of the recording of facts and inforraation concerning the conditions exist- ing at the point and its immediate vicinity. The Survey Form contained space for recording observations on the nature of the vegetation, the water, and the terrain, as well as such items as the presence of animals, people, houses, mud any Other pertinent inf omation. The information required about each collection point was divided into fifteen groups. Each group contained information of one type, and all, together, formed the basis upon which selection of points, as permanent collection points, was made. The facts obtained from these Survey Forms were used, not only in determining what areas were selected as permanent collection points, but in the tabulation 'and analysis of tho prevalence of mosquitoes in re- lation to various factors in the environment. Daily Work of Field Personnel The crew member in each town proceeded on foot along public roads to the designated collection points. During the first visit to- a collection point, the crew member made out a survey sheet,. He, thereafter, proceeded to collect adult mosquitoes, as described in detail in ’’Instructions for Catching Adult Mosquitoes”. In general, the adults wore caught by a net carried by the crew member or by simply placing the killing tube over'the resting mosquito for a few minutes until the mosquito was killed. The adults were then placed between layers of cellulose in a pill box, A label was filled out, folded and 33 placed inside the box# Larvae were collected by the method described in ”Instructions for Collecting Larvae”. Water containing the larvae was dipped from puddles, streams, ponds, marshes, etc,, with a largo dipper. The larvae were then carefully sucked up into a medicine dropper and transferred to a small vial. After the crew member had collected several larvae, ho filled the vial to about one inch from the top and added five drops of 40/o formalin dyed a light blue for easy identification. The identi- fication slip, marked with the number of tho collection point and date of collection, was inserted and the vial corked, A label was filled out, folded, rolled about tho vial and secured with a rubber band. If no specimens of either adults or larvae were found, the crew filled in a pink label for the collection point. Upon completion of work at one collection point, the crew member proceeded on foot to tho next. If there were more than one type of water collection in a collection point, a collection of larvae was made in the different kinds of water. Each collection was placed in a separate vial and separately labelled. For example, a pond, a running stream and a tree-hole were three different types of water. Collections were made from all three, the specimens being placed in three separate vials, each with its own label. Three different typos of labels were used: (l) Label for Reg- ular Collections, white; (2} Label for Regular Collections, pink; and (3) Label for Occasional Collections, All throe labels were used by the field collectors and are discussed in the bulletin "Training Course for Field Personnel", Tho white label for Regular Collections was used for those made at permanent collection points. The pink label was used for permanent collection points but was filled out only when no specimens were found. It was used only by the \T, P, A, personnel and it was intended as a chock on the individuals. The label for occasional collections was used for specimens which wore picked up at places other than regular collection points, Host of the volunteer collections we re of this type; and, consequently, this label was the one most frequently used by the volunteers. As in the case of the survey sheet, tho labels contained' several lists from which the collector selected tho appropriate items. The direction of the wind was easily established as the collector pos- sessed a map of the town. Only the cardinal points of the compass, 'with but one subdivision, were used in the description of wind direction. Complete instructions for the use of the different labels were supplied each collector. During the first two weeks of the Survey, while the field personnel was being trained, collections were small in number. Collec- tions were started on a state-wide basis during the first week of July, Toward the end of July the crews were familiar with their districts and collection points were established in most of the towns. By the end of July, with few exceptions, collections were being made from most of the towns in the Commonwealth, Thereafter, the number of collections continued to increase and reached a maximum late in September, The months of May, June and July were exceptionally dry. The normal rain- fall for those months is 10.25 inches. In 1939 there fell only 6.53 34 inches of rain, or about two-thirds of the normal. Many marshes, small ponds and streams dried up, others decreased in size, and puddles and small collections of water were practically non-existent. This lack of rainfall was reflected in a diminution in the number of mosquitoes. Where, in 1938, mosquitoes were unusually prev- alent, due to the heavy rainfall throughout the summer and 'early autumn, in 1939 mosquitoes were comparatively scarce. Although there are no established data on the prevalence of mosquitoes in 1938, the observa- tions of mosquito control men may be taken as authentic evidence. These workers, as well as the residents, observed that during 1938 mosquitoes were unusually prevalent throughout southern Massachusetts. In 1939, on the other hand, mosquitoes wore so scarce that vacationists reported they were able to sleep in the open without screens or netting. This luxury of sleeping under the stars without fear of mosquitoes, was a blessing which had not been given for many years. Collections of mosquitoes were, therefore, quite difficult during July, As many ponds, marshes and streams dried up, new collec- tion points had to bo established. Fortunately, in August, rainfall was slightly above normal. This increased rainfall was reflected in the increased prevalence of mosquitoes. The number of collections in August increased and in September reached a maximum. However, there was not enough rain to compensate for the three preceding dry months and water collections began to decrease again in size and number. At no time during the summer and autumn of 1939 was there a normal predom- inance of mosquitoes. It is our distinct impression and that of many of the mosquito control men, that mosquitoes throughout 1939 were unusual- ly scarce. There is one exception to this observation from Cape Cod where, during 1938, there were many heavy rains in this region. Ponds filled up, and in the spring of 1939 were at an unusually high level, in some in- stances higher than any recorded in the past twenty-five years. In thia region, Mansonia perturbans, a vicious biter, was unusally prevalent, especially in the spring and early summer. The number, of collections in the different districts varied greatly. The apparent non-existence of certain species in certain dis- tricts may be accounted for by the difficulty of obtaining qualified personnel in those areas. Other factors which influenced collecting were the size of the area to bo covered, the nature of the terrain and the meteorological conditions. An attempt to evaluate the completeness of collections and the influence of these various factors is made in the analysis of the data. 35 CHAPTER VII TECHNICAL PROCEDURES IDENTIFICATION OF SPECIMENS The identification of collections was carried out by the entomological staff consisting of a consultant en- tomologist, a chief entomologist, four senior entomologists, four jun- ior entomologists and several laboratory assistants. The consultant entomologist did not do routine identification, but examined specimens which were unusual or difficult to identify. Those which were thought to be new species, insofar as their collection in the Commonwealth was concerned, were sent to the United States Department of Agriculture en- tomologists in Washington, In this way, all unusual specimens of species which were collected for the first time in the Commonwealth were identi- fied not only by the consultant entomologist, but also by the federal entomologists. The chief entomologist was directly in charge of the identi- fication. He was responsible for the assignment of work to the various entomologists. Like the consultant, he did not do routine identifica- tion except when there was an accumulation of specimens. His first function was the direction of the identification work and examination of unusual specimens. The routine identifications were done by the senior and junior entomologists. Most of the identification of adults was performed by the senior entomologists whereas the larvae which were more easily recognized were identified by all the workers. It is estimated that the rate of identification was fifty collections per man per day for adults, and one hundred twenty per man per day for larvae. These estimates are based upon a man working alone and in conjunction with such other tasks as v/ere assigned to him. "/lien a laboratory assistant aided the entomologist, the number of specimens which could be identified in the course of a day was more than doubled. This was especially true 7/hen the men became experienced in the handling of specimens. Towards the end of the Survey, as many as one hundred fifty collections of adults, and two hundred fifty to three hundred collections of larvae were examined by a single man. Because of the Survey’s interest in obtaining data on the distribution and prevalence of all species of mosquitoes,it vans nec- essary to identify every specimen which reached the laboratory. The specimens arrived once a week, on Fridays, when the Area Supervisors came to Boston to attend weekly conferences. The specimens from-each district were kept in separate containers; This facilitated the iden- tification as most of the collections coming from the same district were of the same general character, that is the some species predominated. The adult specimens reached the laboratory between layers of cellotex, in small pill boxes. The label accompanying each, had been inserted between the drawer and the casing of the pill box. On opening the box the label was removed and unfolded. The identification data on the specimens was written on the reverse side of the label. The labels 36 from each district for each week were kept in one bundle and shipped to the filing room. Similarly, labels around the vials containing the larvae were unrolled and the identification data noted on the reverse side. These labels were handled in the same way as those for the adult collections. The identification data recorded on each label consisted of the names of the genus and species, the letters "A" and "L" for adults and larvae respectively, the number of specimens of each and the name of the person who made the identification. If the specimens were un- identifiable, either because of deterioration or lack of maturity, a note to this effect was made. If the specimen were not a mosquito, the letters "IIM" were placed on the bank of the label. In this way it was possible to use but one form, containing both the collector's and the identifying data. The transcription of this information on summary sheets was much less complicated than it would have been, had two forms been used. In addition, in case of any doubt as to identific- ation data, it was possible to check back and ascertain who had made the identification. IDENTIFICATION KEY The technique of mosquito identification consists mainly of a process of elimination. The identification key for adults and larvae notes certain characteristics as either present or absent. The presence or absence of a particular characteristic determines whether the mosquito is further identified in one group or another. This same method is followed through until the absence or presence of a single characteristic determines the species of the mosquito. At the beginning of the Survey, identifications were based upon Tulloch’s key which was published in 1,930. V/hen about one hundred thousand specimens had beep identified, enough do,ta was collected to revise this' key, and, as one of the objectives of the Survey, a new key was compiled and published. This new identification key was used through- out the remainder of the Survey, It is adaptable to use in New England and perhaps in New York as well, Special Mosquito Collections In addition to the routine identification of specimens and the revision of the identification key, the entomologists had several other duties. Special collections of unusual specimens espec- ially those found for the first time in the state, wore made by the entomo legists. Whenever a 17, P, A. collector found an unusual specimen he was asked to revisit the location of the collection point for additional spec- imens, At the seme time an entomologist was sent to this area to make further collections at the seme place and in the surrounding area, in an attempt to obtain large numbers of specimens. The entomologists attempted to collect mosquitoes naturally in- fected with equine encephalomyelitis. Those attempts were made whenever a case of this disease was reported to us by the State Department of Ag- riculture. Light and animal baited traps were taken to the place from which the case had been reported. However, the disease was so rare that cases were not reported until the afflicted horse had died. 37 Consequently, wo arrived at the farm or stable where the animal had been quartorod too late to collect the mosquitoes whose bite was re- sponsible for the infection. This lapse of tine was one of the reasons why our collections were a failure. The majority of these cases wore reported to us late in the mosquito season and wo were unfortunate enough to have meteorological conditions which were unfavorable to mosquitoes. As a matter of fact, very few specimens wore collected by use of animal- baited and light traps on these occasions, and, therefore, we could not expect to collect naturally infected mosquitoes. In conclusion, these endeavors to collect the mosquito vector which had been infected natural- ly with equine encephalomyelitis could not be considered a fair trial because of the lapse of time which had occurred between the onset of the disease and the arrival of the entomologists, and because of the small number of mosquitoes which were collected during these endeavors. Additional light trap collections were made from time to time in several parts of the state. These collections which were made prin- cipally at the earlier part of the season were quite satisfactory and on one such collection over one thousand individual specimens were obtain ed in the course of on evening. However, when there were unfavorable meteorological conditions such as a fresh wind or a drop in temperature, collections were poor. The entomologists assisted in the supervision of the methods of collection used by the TV, P. A. personnel. Periodical trips were made to the various districts in an attempt to check on the methods - which were being used in the field by the individual workers and to instruct and assist them in improving their technique. This staff like wise assisted in the checking of the surveys of collection points, and wore sent out on special chock trips whenever we had cause to suspect that specimens were not authentic. Several permanent collections of adults and larvae were made. These were intended as a permanent record of the collections made by the Survey and some were sent to various institutions which had request- ed such collections, Hypopygial mounts were mr.de of many of the species. All these.collections are available for future use in the identification of specimens and serve as a sure check on any work which may be carried out in the future, . In all, the entomologists examined and identified forty nine thousand collections, consisting of two hundred seventy eight thousand specimens. This figure includes the collections made by volunteers. It is our opinion that the entomological staff of a survey of this type should be quite large because its functions are so varied and important to the success of the survey as a whole. When organizing new surveys it is our recommendation that allowances bo made for a greater number of entomologists. 38 CHAPTER VIII ANALYSIS OF DATA Posting Sheets In order to facilitate the posting of the data, we devised a summary sheet, which could be used for the original record- ing of the data and for the final summarizing. On this sheet there were spaces for all the items on both sides of the label. The names of the mosquitoes were arranged alphabetically by genus and species. All the mosquitoes that were known to occur in Massachusetts were in- cluded and room was left for such mosquitoes as might be found for the first time in Massachusetts during the course of the Survey, The in- formation from the front'of the label was entered on this sheet accord- ing to the attached code. The identification data on the opposite side of the label was entered in two ways, by number of specimens of each species. Adult or Larva, and by the number of collections of each species. The labels were filed aphabetically by counties and towns, numerically by collection point numbers and thereafter chronologically by weeks. Each label was entered in this order upon the sheets as a separate entry. There was one summary sheet for each collection point. As collections were made at a given collection point on the average of once a week, there was one entry per week for each collection point on this sheet. If there were more than one entry, these were added every week and the sum written in red on the following line. The weekly totals from the collection point summary sheet were transferred to a town sheet of which there was one for each city or town in the Commonwealth, These entries in turn were added every week and transferred to a town summary' sheet. In this way a running summary of the total findings in a town for the season could be obtained from a single record sheet. Occasional collections were entered on the town summary sheet and added to the collec tion point totals. In this way, the town summaries included all the col- lections made in the town. A separate account was kept for the W, P, A, collections and the volunteer collections. The two groups were finally combined on a new sheet entitled "Combined Summary of Town", This sheet contained the final summary of the project collections of mosquitoes in the town. At the end of the season, the combined town summaries were added and this accumulative result was the total collections of mosquitoes made in that town during the season. These accumulative results were transferred to" county summary sheets where the totals for the counties were determined. Similarly, the counties were totaled on a state sheet which was the to- tal number of mosquitoes and the total number of collections for the Com- monwealth throughout the season. Punch Card Analysis In order to analyze this large number of collec- tions, id was necessary to resort to the Remington Rand Punch Card Method, A ninety column punch card with ten items to a column was used. Two sets of cards were employed for the analysis of data and therefore two sepa- rate codes were used as these sets were entirely independent of each other. Both codes are attached. The Town Code and the Collection Point Code are different except for the method of recording the collections of the vari- ous species. MOSQUITO SURVEY 39 DEPARTMENT OF PUBLIC HEALTH CODE FOR SUMMARY SHEET NO. OF COLLECTION POINT Example: 030712 03 indicates Barnstable County 07 u Town of Falmouth 12 ” Number of Collection Point as noted on map. WEEK OF YEAR NO. OF MONTH DAY IN MONTH HOUR A.M, OR P.M. CONDITION OF AREA: 0 - No Observation 1 - Very dry 2 - Dry 3 - Moist 4 - Wet 5 - Submerged DIRECTION OF YfIND: 0 - No Observation 1 - N 2 - N E 3 - E 4 - S E 5 - S 6 - SI 7 - W 8 - N W VEGETATION: 0 - No Observation 1 - Dead 2 - Withered 3 - Drying 4 - Healthy 5 - Succulent PREVALENCE OF ADULTS: 0 - No Observation 1 - None 2 - 1 to 5 3 - 6 to 25 '4 - Scores 5 - Hundreds 6 - Thousands 7 - Hundreds of Thousands WEATHER; 0 - No Observation 1 - Sunny 2 - Cloudy 3 - Foggy 4 - Misting 5 - Raining PREVALENCE OF LARVAE: 0 - No Observation 1 - None ' 2 - 1 to 5 3 - 6 to 25 4 - Scores 5- - Hundreds 6 - Thousands 7 - Hundreds of Thousands WIND: 0 - No Observation 1 - None 2 - Mild 3 - Moderate 4 - Strong 40 SPECIMENS COLLECTED FROM WATER COLLECTIONS NATURAL 00 - 25 04 Ditch 08 Fresh Swamp 10 Pond 11 Puddle 12 Quarry 15 Salt Marsh 16 Stream 17 Stump Hole 19 Tidal Flat ARTIFICIAL 26 - 50 26 Barrel 27 Bird Bath 28 Bucket 30 Cistern 32 Dish 33 Fountain 35 Flower-pot container 40 Roof Gutter 45 Tin Can 46 Troughs 48 Watering Pot OUTDOORS 51-75 56 Dump 60 Field 62 Lakeside 63 Meadow 64 Marsh ■66 Riverside 66 Road • 67 Seashore 68 Shrubs 69 Trees 73 Weeds 74 Woods 75 Yard BUILDINGS 76 - 100 78 Barn 80 Chicken Coop (Hen House) 82 House 86 Other Outhouse 86 Stable 90 Cattle • 91 Horses. 92 Mules 93 Sheep 99 Man Recording by Genera, Species Enter actual number under each A - Adults L - Larvae Under unclassifiable enter - actual number Other species - insert name of species and’enter actual number, after consultation with Technical Director. REMARKS CHANGES 00 - 25 02 Burned over 05 Construction 10 Dam opened 11 Dam closed 12 Drained 15 Harvested 20 Oiled 21 Other Mos..Control Measures 22 Pastured 23 Plowed 24 Timber cut .NJ.MALS 26 - 50 27 Chicken 28 Cattle 29 Dogs 30 Domestic Ducks 31 Grouse 32 Hogs 33 Horses 34 Mules 56 Partridges 36 Pheasants 37 Pigeons 39 Sheep 45 Wild Ducks HUMANS- 51 - 75 61 Fisherman 64 Harvesters 70 Picnickers 53 Bathers 55 Campers 60 Farmers COLLECTION POINT CODE 41 Column 1 & 2) COUNTY NUMBER 3) Barnstable 14) Berkshire 5) Bristol Counties are numbered from 1 to 14 as follows: 2) Dukes 12) Hampshire 6) Norfolk 8) Essex 9) Middlesex 4) Plymouth 11) Franklin 1) Nantucket 7) Suffolk 13) Hampden 10) Worcester 3 & 4) TOWN NUMBER The towns are numbered alphabetically in each county, beginning with 1. 5 & 6) WEEK OF YEAR The weeks arc numbered chronologically begin ning with the first week of the year. 7 & 8) NUMBER OF DRAINAGE AREA Salt Water 11) Capo Cod 12) Center Coast 13) East Coast 14) Ipswich 15) Islands 16) South Coast Merrimac 31} Assabct 32) Concord 33) Merrimac 34) Nashua 35) Sudbury Connecticut 51) Chicopee 52) Connecticut 53) Deerfield 54) Farmington 55) Millers 56) Westfield Boston Harbor 21) Charles 22) Mystic 23) Neponset Rhode Island 41) Blackstone 42) French 43) Taunton 44) Ten Milo 45) Quinebaug Berkshircs -61) Hoosic 62) Housatonic 13)Water Containers 0) None 1) Not marked 2) Artificial pool (pond) 3) Barrels 4) Birdbath or flow- er pot 5) Cesspools & over- flow 6) Cistern (open) 7) Dump 8) Water trough 9) Other 9)Contour 0) Not marked 1) Le ve 1 2) Valley 3) Hillside 4) Hilltop 5) 1 & 2 6) 1 & 4 7) 2 oc 3 8) 3 & 4 9) Other 11)Natural Water Colls. 0) None 1) Not marked 2) Marsh & swamp 3) Pond or Lake 4) Puddle 5) River or Stream 6) Rocky crevice 7) Run. & Still 'Water 8) Tidal Flat 9) Other 10)Nature of Terrain 0) None 1) Not marked 2) Cultivated fields 3) Meadow pastured 4) Meadow unpastured 5) Rocky 6) Woods 7) Meadow & woods 8) Meadows os cul, fields 9) Other 14)Vegetation at Yfatcr Edge 0) None 1) Not marked 2) Cat-tails & reeds 3) Pickerel weeds 4) Arrow heads 5) Bulrush 6) Marsh grass 7) Cat-tails,reeds & other 8) Marsh grass & other 9) Other 12)Artificial Coll. 0} None 1) Not marked 2) Cranberry bog 3) Excavation 4) Quarry 5) Sand pit 6) Root Hole 7) Tree Hole 8) Well 9) Other 42 Column COLLECTION POINT CODE 15) Vegetation in Water 0) None 1) Not marked 2) Lily pads 3) Algae 4) Duckweeds 5) Water mosses 6) 2 & Other 7) & Other 8) 4 & Other 9) Other 19) Weeds & Underbrush 0) None 1) Not marked 2) Bushes 3) Hedges 4) Weeds over 3 feet 5) Weeds under 3 feet 6) 4 & 5 7) 2 & 5 8) 2 & weeds any kind 9) Other Non-Susceptible Birds To) 41) Chickens 42) Domestic Ducks 43) Gulls 44) Wild Ducks 45) Turkey 46) Several 47) Other 48) 49) 16) Character of Water 0) None 1) Not marked 2) Brown 3) Colorless 4) Muddy 5) Floatage 6) 5 & 2 7) 5 & 3 8) 5 & 4 9) Other 20) Animals in Area 21) dO) ftone 01) Not marked 22 )Buildings in Area 0) None 1) Not marked 2) Less than 5 3) 6-25 4) 26-100 5) More than 100 or — factories 6) Stables & others 7) Poultry houses 8) Stables Susceptible Birds 10) 15 &' 16 11) Horses 12) Mules 13) Horses & Mules 14) Horses & Mules & Susceptible Birds 15) Horses & Non-Sus- •- ceptible Birds 16) Horses & Non-Sus- coptible Mammals 17) 14 & 15 18) 14 & 16 19) 14, 15 and 16 17) Character of Bottom OjlJono' 1) Not marked 2) Earth or Mud 3) Leaves 4) Rock 5) Sand 6) 2 & 4 7) Vegetation 8) 3 & Other 9) Other 23 )Mosquito Control Measures d) None 1) Not marked 2) Diking 3) Ditching 4) Filling 5) Oiling s 6) 2 & 5 7) 3 & 5 8) 4 & 5 9) Other Susceptible Birds 20) All 20*s,30’s & 40’ 21) Young Chickens 22) Pheasants 23) Pigeons 24) Cowbirds 25) Red wing,Blackbird 26) Sparrows 27) Several Susceptible 28) Susceptible & Non- Susceptible Birds 29) Susceptible Birds & Non-Susceptible Ani mals 18) Trees 0) None 1) Not marked 2) Evergreen 3) Hardwood 4) Willows 5) Fallen trees 6) Burned trees 7) 2 & 3 8) 5 & 2 or 3 9) Other 24)Prevalence of Mos- quitoes 0) None 1) Not marked 2) A.scarce & no L, 3) A,numerous & no L. - 4) L,scarce & no A 5) L,numerous & no A, 6) A,scarce & L.scarce 7) A,scarce & L.numerous 8) A,numerous & L.scarce 9) A*numerous & L.numer- ous Non-Susceptible Mammals 30) Small rodents 35-)~ Rodents 31) Cats 36) Sheep 32) Cattle 37) Several 33) Dogs 38) Other 34) Hogs 39) Any 30 & Any 40 43 COLLECTION POINT AND TdTN CODE Columns 25-55 & 57-80, also 85-90, use this system* 1) 1 collection 2) 2-5 collections 3) 6-10 collections 4) collections 5) collections 6) collections 7) collections 8) collections 9) Over 100 collections €0) Anoph.punotipennis L 61) Anoph.quadrimaculatus A •62) Anoph.quadrimaculatus L 63) Anoph.tfalkeri A 64) Anoph .walkeri L 65) Culex apicalis A 66) Culex apicalis L 67) Culex pipiens A 68) Culex pipiens L 69) Culex salinarius A 70) Culex salinarius L 71) Culex territans A 72) Culex territana L 73) Mansonia perturbana A 74) Mansonia perturbans L 75) Theobaldia melanurus A 76) Theobaldia melanurus L 77) Theobaldia morsitans A 78) Theobaldia morsitans L 79) Uranotaenia sapphirina A 80) Uranotaenia sapphirina L 25) Aedes atropalpus 26) Aedes atropalpus 27) Aedes aurifer 28) Aedes canadensis 29) Aedes canadensis 30) Aedes cantator 31) Aedes cantator 32) Aedes cinereus 33) Aodes cinoreus 34) Aedes dorsalis 35) Aedes dorsalis 35) Aedes excrucians 37) Aedes excrucians 38) Aedos fitchii 39) Aedes fitchii 40) Aedes hirsutoron 41) Aedos hirsutoron 42) Aedes intruders 43) Aodes intrudons 44) Aedes sollioitans 45) Aedes sollioitans 46) Aedos stimulans 47) Aedes stimulans 48) Aedes taoniorhynchus 49) Aedes taoniorhynchus 50) Aedes triseriatus 51) Aedes triseriatus 52) Aodes vexans 53) Aedos vexans 54) Aedes implacabilis 55) Aedes implacabilis 56) Vectors 5) Hot'present 1) Present ITames of Vectors Aedes atropalpus Aedes cantator Aedes sollioitans Aedes triseriatus Aedos vexans 57) Anophimaculipennis 58) Anoph imaculipenni s 59) Anoph.punctipennis A L A A L A L A L A L A L A L A L A L A L A L A L L A •i i> L il L 81) Others 1) Aedes trichurus A 2) Aedes trichurus L 3) Aedes trivittatus A-L-7 4) Anoph.crucians L 5) Aedes punctor A 6) Aedes punctor L 82) Others 1) Psorophora ciliata A 2) Psorophora ciliata L 3) Psorophora columbiae L 83) Others 1) Orthopodomyia L 2) impatiens A 3) Theobaldia inornata A 4) Wyeomia smith! i L 84) Others 1} Chaoborus 2) Corethrella 3) Eucorethra 7) Chaoborus 4) Mo chi onyx Mo chi onyx ■5) Dixa 6) Chaoborus & Dixa 85) Aedes unidentified A 86) Aodes unidentified L 87) Anoph.unidentified A 88) Anopluunidentifiod L 89) Culex unidentified* A 90) Culex unidentified- ’L A L A 44 TOTTN CODE Column 2) COUNTY NUMBER Counties are numbered from 1 to 14, the counties are numbered as follows; 3) Barnstable 14) Berkshire 5) Bristol 2) Dukes 8) Essex 11) Franklin 12) Hampshire 13) Hampden 9) Middlesex 1) Nantucket 6) Norfolk 4) Plymouth 7) Suffolk 10) Worcester 4) TOWN NUMBER The towns are numbered alphabetically in each county beginning with 1, 5-) WEEK OF YEAR The weeks are numbered chronologically begin- 6) ning with the first week of the year. 7) NUMBER OF DRAINAGE AREA 8) The drainage areas are numbered as follows; Salt Water 11) Capo Cod 12) Central Coastal lo) East Coastal 14) Ipswich 15) Islands 16) South Coastal Merrimao 31) Ascabet 32) Concord 33) Merrimac 34) Nashua 35) Sudbury Connecticut 51) Chicopee 52) Connecticut 53) Deerfield 54) Farmington 55) Millers 56) Westfield Boston Harbor 21) CharIds 22) Mystic 23) Neponset Rhode Island 41) Blackstone 42) French 43) Taunton 44) Ten Mile 45) Quinebaug Berkshires 61) Hoosic 62) Housatonic 9) Deviation of 1939 10) Precipitation From Average 11) Deviation of 1939 12) Precipitation From 1938 9 10 5) 0) Zero 1) l) Under 5.1 ()0 2) 5.1-10.0 3) 10.1-15.0 4) 15,1-25.0 U) 25.1-40.0 6) 40,1-55.0 7) 55.1-70,0 8) 70.1-100.0 9) Over 100 11 12 5) 0) Zero 1) 1) Under 10,1 9)0 2) 10.1-25.0 3) 25.1-40,0 4) 40.1-55.0 ■5) 55'. 1-70.0 6) 70.1-85.0■ 7) 85.1-100.0 8) 100.1-200 9) Over 200 45 TOWN CODE 13) Deviation of 1939 14) Temp. From Ave. Temp. IS • ' TT K "5j 0) Zero 1)' 1) Zero- 0.50 9)0 2) 0.51- 1.00 3) 1.01- 1.50 4) 1.51- 2.00 5) 2.01- 3.00 6) 3.01- 5.00 7) 5f01- 7;50 8) 7.51-10.00 9) 0ver-10. 19) Total Number of Larval Collection 1) 1 2) 2 - 5 3) 6 - 10 4) 11- 15 5) 16- 20 6) 21- 30 7) 31- 50 8) 51- 100 9) Over100 23) % W»P«A, Larvae 1) Zero - 5 2) 6 - 10 3) 11 - 15 4) 16 - 20 5) 21 - 30 6) 31 - 40 7) 41 - 50 8) 51 - 75 9) 76 - 100 15) Deviation of 1939 16) Temp. From 1938 Temp. 15 TS "Sj O^^ero 1) 1) Under 0.51 9)0 2) 0.51- 1.00 3) liOl- 2.00 4) 2.01- 5;oo 6-) 5.01- 7.50 6) 7.51-10;00 7) 10.01-12.50 8) 9) Over-15 20) Total Number of Adult Specimens 1) 1 2) 2 - 5 3) 6 - 10 4) 11- 20 5) 21- 30,. 6) 31- 50 7) 51- 100 8) 200 9)Over 200 24) Number of Coll Points 1) 1 2) 2 3) -5 - 5 4) 6 - 8 5) 9 - 11 6) 12- 18 7) 19- 31 8) 32- 48 9) 0ver48 17) Direction of Pre- vailing winds 0) Wone 1) Not marked 2) N 3) NE 4) E 5) SE 6) S 7) sw 8) W 9) m 21) Total Number of Larval Specimens 1) 1 2) 2-5 3) 6 - 10 4) 11- 20 5) 21- 50 6) 51- 100 7) 150 8) 200 9) Over 200 18) Total Number of Adult Collections 1) 1 2) -2- - 5 3) 6 - 10 4) 11- 15 -&) 16- 20 6) 21- 30 7) 31- 50' 8) 51- 100 9) Over100 22) % W.P.A. Adults 1) -Zero - 5 2) 6 - 10 3) 11 - 15 4) 16 - 20 ■&) 21 - 30 6) 31 - 40 7) 41 - 50 8) 51 - 75 9) 75 - 100 Columns 25 to 90 are the same in this code as in the Collection Point Code, See Page 43 46 Town Code’ The weekly summaries of collections in every town included both W, P, A. and volunteer collections and were coded according to the accompanying code and then punched on a set of cards. The code enabled an analysis of the geographical distribution of the various species, the relation of meteorological conditions to the distribution of the species, the geographical distribution of the vectors of the disease, and the distribution of mosquitoes according to rivers and drainage areas.’ This code covered all collections made during the course of the Survey. As a card was punched for every week during which collections were made, this set of cards enabled us to determine the seasonal dis- tribution and prevalence of the various species. An attempt has been made to do this on a quantitative as well as a qualitative basis;. Collection Point Code The collection point code was applied to the data obtained from! two sources: (l) Survey of regular collection points, (2) Seasonal summaries for collections made at the collection points. The code enabled the compilation of information concerning the influence of environmental factors upon the geographical distribution and prev- alence of mosquitoes. This code made possible the correlation of various environmental factors which characterized the breeding places of certain species of mosquitoes. It was likewise possible to determine the distri- bution of mosquitoes according to counties and watershed areas. In order to prevent, mistakes between the code sheets and the punch cards of the two separate analyses, the town code analysis was made with white code sheets and two sets of c*rds, one pink and the other white. The collection point code analysis was made with yellow code sheets and the two sets of cards, blue and green. It was necessary to have these duplicate sets of punch cards as the establishment of the various correlations required more sorting than one set of cards could stand. Checking As in all statistical analyses of this type, the avoidance of errors was paramount throughout the analysis of the data. Therefore, the posting, the coding and the punching was checked and re-checked in order to obviate as many mistakes as possible. When the posting was first begun, a check rovealed approximately a ten percent error. With experience this was reduced to five, A spot re-check of the posting revealed less than one half of one percent error. In coding, the initial error was smaller, amounting to about three percent. On a spot re-check, this was found to be about one in six thousand. The punch cards" them- selves were chocked against the code sheets by the use of a Remington Rand Interpolator which printed the numbers punched on the cards them- selves, These in turn were checked with the code sheet. We found on an initial chock on error of approximately two percent. On a spot re-check this error was reduced to about one half of one percent and very few errors were found during the sorting of the cards. The time required for the coding of both sets was about four weeks. The punching and checking of the cards required about five weeks., exclusive of the time required in the servicing'of the machines. The sorting of the cards was completed in six weeks. 47 CHAPTER IX SAMPLING THE MOSQUITO POPULATION In a survey of this type, only a relatively small sample of the entire mosquito population can be studied. Therefore, in order to be in a position to generalize about the whole, the sample has to be rep- resentative of the population. In this Survey, the selection of samples has been carefully avoided. The collection of specimens was made in such a way as to insure true random sampling without relation to any factors except two. The first factor was the limitation of the area in which a collector was to obtain his samples. The town or city was arbitrarily picked as the most practical basic area unit. The other factor influ- encing the collection was the limitation of the number of specimens of larvae to ten per sample. This number was chosen as the practical limit which could be identified by the entomological staff. Moreover, it was felt that in ton specimens from any one place, there would bo ample op- portunity for true sampling of the species existing in that place. Al- though efforts were made to obtain specimens from the same breeding pla- ces at regular intervals throughout the year, all places whore mosquitoes were found breeding were sampled. Moreover, only one sample was submit- ted from each breeding place. Under these conditions, the mosquitoes represent a true random sample of the mosquito population. Duration of State-Wide Survey The Survey1s training course for the W, P, A, supervisors, foremen and assistant * foremen was completed on June 23rd, During the following week the U,P,A, crows were assembled, and training of these men'was underway. By the first of July most of the crows were operating on a full schedule, and by the middle of July, about one-half of the towns were being covered by the Survey collectors. At the end of July the project was in full swing, and collections were made throughout the state. The number of towns in which collections were made every week is charted in Figure II, State-wide collections wore continued for a period of thirteen weeks throughout the months of August, September and October, Representative collections throughout the state were made dur- ing the month preceding this complete state coverage. In this way, the Survey made collections throughout the Commonwealth during the season when equine encephalomyelitis had occurred in 1938, Collections were continued by the Survey through the first week of December, but these were limited to Dukes County, which, because of its geographical situ- ation, has a longer mosquito season. Mosquito Collections For the purpose of this analysis, a mosquito col- lection is defined as the finding of either one or more adults or one or more larvae of one species of mosquitoes in one location. If, in a single sample, there are more than one species of larvae, this sample is counted as a separate collection for each of the species represented. By defini- tion, it is impossible to have both adults and larvae in the same col- lection, as the former are collected from a different location than the latter. 48 FIGURE I NUMBER OF TOWNS IN WHICH CC ELECTIONS WERE MADE BY WEEKS 49 Prior to June 15th, all the collections were made by volunteers, who were enrolled by the Division of Communicable Diseases in the Depart- ment of Public Health. By the first of July, the majority of the collect- ions were made by the Survey personnel. Most of the volunteer collections were adults, whilv. those of the Survey personnel were chiefly larvae. The total number of collections is summarized by counties in Table IV. Of the total (49,083) collections of biting mosquitoes 83,5/£ or 40,983 collections were larvae. The proportion of adults to larvae varied in the various counties. In Barnstable County adult collections wore the largest both in number and in percent, representing of the total in that county. In Hampshire County, adult collections comprised only 6% of the total. The weekly collections are charted in Figure III, this group is plotted op throe cycle semi-logarithmic paper. There is an interest- ing rise in tho number ol collections mado each week, to a peak of 5,399 collections in the 40th week (October 1st to 7th), The following week the crews were limited in travel expenses, and two weeks after tho peak the crows were gradually discharged, so that by the 44th woek, only one crew was loft in the field. TABLE IV SUMMARY OF MOSQUITO COLLECTIONS 1939 County Adults Larvae Total Barnstable 1395 2870 4265 Berkshire 477 4507 4984 Bristol 206 1931 2137 Dukos & Nantucket 625 1563 2188 Essex 989 3711 4700 Frr.nkl in 424 2507 2931 Hampden 213 3193 3406 Hampshire 85 1543 1628 Middlesex 1217 6278 7495 Norfolk 464 2514 . 2978 Plymouth 823 4043 4866 Suffolk 158 388 546 Worcester 1024 5935 6959 TOTAL 8100 40983 49083 The number of collections as determined by punch card analysis is summarized in Table V. The totals for adults and larvae, and the percent distribution of each are given by weeks. The percent distribution of adults is plotted in Figure IV, There was a peak during the 24th and 25th week and a gradual decline thereafter throughout the duration of the Survey, Our interpretation of this peculiar distribution of the adult collections rests on the fact that, subsequent to the 28th week (July 9th to 15th), there was a gradual increase in the number of lartfac due to improved breeding conditions, and hence adults grow relatively loss num- erous as more larvae wore collected. 50 FIGUR E III NUMBER OF COLLECTIONS BY WEEKS 51 TABLE V MOSQUITO COLLECTIONS ADULTS, LARVAE, AND PERCENT DISTRIBUTION Week of Year Number Adults By Weeks of Collections Larvae Total Percent of Adults Distribution Larvae 16 0 40 40 0 100.0 17 0 40 40 0 100.0 18 1 22 23 4.3 95.7 19 0 32 32 0 100.0 20 1 22 23 4.3 95.7 21 1 20 21 4.8 95.2 22 2 28 30 6.7 93.3 23 11 31 42 26.2 73.8 24 65 31 96 67.7 32.3 25 186 83 269 69,1 30.9 26 191 127 318 60.0 40.0 27 296 249 545 54.3 45.7 28 512 441 953 53.7 46.3 29 394 804 1198 32.9 67.1 30 515 1002 1517 34.0 66.0 31 460 1500 1-960 23.5 76.5 32 553 2102 2655 20.8 79.2 33 585 2342 2927 20.0 80.0 34 548 3083 3631 15,1 84.9 35 353 3457 3810 9.3 90.7 36 381 3705 4086 9.3 90.7 37 588 4091 4679 12.6 87.4 38 902 4261 5163 17.5 82.5 39 839 4441 5230 15.9 84.1 40 608 4791 5399 11.3 88.7 41 365 2582 2947 12.4 87.6 42 126 1603 1729 7.3 92.7 43 42 461 503 8.3 91.7 44 0 130 130 0 100.0 45 3 87 90 3.3 96.7 46 1 35 36 2.8 97.2 47 4 32 36 11.1 88.9 48 0 32 32 0 100.0 49 1 32 33 3.0 97.0 50 0 17 17 0 100.0 8534 41756 50290* 17.0 83.0 * These figures were obtained from the punch card analysis by interpolation from serial grouping. The actual total was 49,083, 52 ADULT MOSQUITOES PERCENT CE TOTAL COLLECTIONS BY WEEKS OF Y BAR V a5E ACH US E TT5~l939 FIGURE IV 53 Specimens Collected The 49,083 collections of biting mosquitoes compris- ed 278,555 specimens; this is a gross average of 6 (5,7) specimens per collection.# There were 23,719 adult specimens in 0,100 collections, an average of 3 (2.9) specimens per collection. In 40,983 collections of larvae, there wore 254,759 specimens, an average of 6 (6.2) specimens per collection. It is to be remembered that a collection is defined as the finding of any one species; therefore, since more than one species were found at a time the number of specimens per sample was higher than the above figures indicate. Survey collectors were directed not to gather more than ten specimens in any one sample. The number of specimens per field collection was, therefore, between seven end ton. The number of specimens is plotted on throe cycle semi-logarith- mic paper in Figure V, When the Survey started to make collections in the 24th week, the number of adults collected exceeded the number of lar- vae. However, by the 29th week, the number of larvae exceeded by far the number of adults and continued to do so throughout the continuation of the Survey. As has been noted previously, the increased preponderance of larvae is due not to diminished collections of adults but to increased collections of larvae. This correlates with the increased mosquito breed- ing due to improved meteorological conditions as shewn in a subsequent part of this report. Collections Per Square li.il e As the plan of the Survey was made on the city and town as the area unit, the number of collections per square nile was different in the various communities, Collections wore made in all the cities and towns except two. The number of collections per square mile averaged 9 (8,93). The scatter of the towns is charted in Figure VI. The ohemcc variation was 9 * 2S/W or 9 6. This range of 3 to 15 collections per square mile, included 71 percent of the 349 towns in which collections were made. Therefore, there is a greater scatter in this dis- tribution than may be expected by chance. The observed variation was actually 10,4; 9 -VEl or a range from zero to 30 collections per square mile which included all but 8 of the communities. Three reasons are of- fered for the greater scatter of those towns than that which might be ex- pected by chance. In some of the areas, the personnel composing the crews was not adapted to this type of work. The number of collections from the districts covered by those crows was much lower than the average. This factor accounts for those towns in which the number of collections was loss than is to bo expected. Those communities in which the head- quarters of the crews we re located invariably had larger collections and hence the collections per square mile were much greater. Actually, seven of the eight communities that had collections of 30 per square mile or more were these in which the headquarters were located. The third factor which increased this scatter was the contribution made by volunteer collect- ors. The response of these collectors varied greatly in different communit- ies and was responsible for unusually high coverage in the communities of Brookline and those in Barnstable County, Lastly, it must be borne in mind that the towns vary greatly in area. This is a factor which cannot bo practically evaluated. When a community was large, attempts were made to increase proportionately the amount of time during which collections were made each week. 54 figure v ADULTS & LARVAE NUMBER or SPECIMENS BY WEEKS MASSACHUSETTS 193 9 55 Population Effects on Mosquito Collections There were 346 communities in which coll octions wore made "by the Survey personnel throughout the great- er portion of the Survey, The grouping of these communities is made in Table VI. TABLE VI RELATION OF POPULATION TO TOTAL MOSQUITO COLLECTIONS ALL COMMUNITIES Population Number of Mean of Median of Communities Collections Collections Under 500 58 103 85 501 - 1,000 50 112 110 1,001 - 2,500 89 118 100 2,501 - 5,000 63 99 91 5,001 - 10,000 54 129 91 10,001 - 25,000 40 140 120 25,001 - 50,000 14 119 135 50,001 - 100,000 11 118 115 Over 100,000 7 212 245 346 I2T 105 The mean was 121 vdth a bhanco variation ofVl21 or 11, When 121 - 2** is taken as the expected limits of chance variation, all the groups of com- munities fall within this limit except one, that "Over 100,000". The explanation of this phenomena would seem to indicate that collections wore greater in communities of over 100,000 and hence there were more collectors or mosquitoes were more numerous. TABLE VII RELATION OF POPULATION TO TOTAL MOSQUITO COLLECTIONS Communities vdth Routine Collections Only Number of Moan of Median of Population Communities Collections Collections Under 500 35 92 72 501 - 1,000 30 112 110 1,001 - 2,500 86 115 112 2,501 - 5,000 63 99 91 5,001 - 10,000 48 102 83 10,001 - 25,000 33 120 110 25,001 - 50,000 12 102 105 50,001 - 100,000 8 90 90 Over 100,000 1 45 45 Total 3l6 106 Too 56 DISTRIBUTION OF CITIES & TOWNS BY NUMBER Of MOSQUITO COLLECTIONS PER SQUARE MILE 1 1 1 FIGURE VI 57 Mien a correction is introduced, the real facts are to be obser- ved. The elimination of those communities where collectors were unusually active, indicates that there was no significant association of population and the number of collections made in the community. Table VII summarizes the data. The moan now becomes 106 with a chance of 106 - 10.3. The chance variation of 106 - 2vTb6, a range of 85 to 127 includes all population groups except those under 500 end over 100,000. Generally speaking, the communities with loss than 500 population are inaccessible to collectors because of lack of roads arid easy means of transportation, Ginco there is only one community in the group over 100,000, this cannot bo taken as a sample cf the whole, especially when it is recalled that the ether seven had an average of ever 250 collections. Those seven were eliminated from this group because they ■wore- the headquarters cf seven of the crew, and hence subject to more collecting than was routine. It is apparent that there was no statistical relation between the population cf the communities end the number cf collections made in them. Those facts taken into consideration support the evidence given above, that the samples of mosquitoes collected by the Survey are a true random and unsclectod sample, and, therefore, are representative of the mosquito population cf the state. 58 CHAPTER X HET120R0L0GICAL CONDITIONS A!\TD MOSQUITOES There are twenty-six meteorological observation stations scat- tered throughout the Commonwealth which send their reports to the United States Weather Bureau in Boston, Weather data was obtained from them during the Survey. With the help of the chief of the T'oathor Bureau, we divided the state into areas surrounding each weather station in such a way as to obtain the best data on meteorological conditions in each community. Topography end meteorological data were factors to be consid- ered in the formation of these areas. Rain The relation of rainfall to mosquito collections is charted in Figure VII. The initial rise in collections during the 23rd to 25th week was due to the increased organization of tho Survey, During the ensuing month and up to the beginning of the 31st week, the W, P. A, personnel was gradually penetrating into all communities in the state, Tho largo increase in collections during July and the first week in August was due, not to an increase in personnel, but to an increase in tho number of mos- quitoes, However, the la st throe weeks of August were rather dry, and collections gradually levelled off. It was confirmed by field observations that there is an increase in mosquito breeding one week after a heavy rain, however, the ponds and streams wore so low that many remained below normal levels throughout the season. The association of rain and mosquitoes becomes more apparent on comparison of the 1938 end 1939 precipitation data. During 1938, Figure VIII, there was an accumulation of 11,7 inches of rain above normal, an excess of 26%, That year mosquitoes wore unusually prevalent throughout the state. In 1939, there was a deficit of 5,5 inches of rain, 13%, below normal. Mosquitoes wore at no time as prevalent as in other years. The precipitation of the summers of 1938 and 1939 is compared with the normal in Figure IX, The 1938 rainfall was far above normal in June, July and September, in 1939 rainfall was below normal throughout the mosquito season. It nay bo well at this time, to point out the association of rainfall to equine encephalomyelitis as observed in tho 1938 outbreak. If the precipitation data is plotted similarly, Figure X, wc find that July was a wot month. When the reported deaths are plotted on tho same chart, it becomes evident that the peak of the outbreak occurred in the middle cf August, or throe to four weeks after the heavy rains of July, These facts correlate with the mosquito transmission cf the disease. Tho development of tho mosquito from egg to adult requires from one to two weeks. Upon emerging, tho female must bite an infectious horse and undergo an extrinsic incubation period; if it survives, it must bite a second horse in order to transmit the disease. Assuming that the mos- quito will not bite again for about throe cr four days after its first meal, a total of two to throe wpeks would elapse before a horse could be infected. As tho curve plotted in Figure X was cf deaths in horses, several days of illness of tho animal must bo included. It becomes appar- ent, therefore, that a definite tine relationship exists between heavy 59 rainfall and outbreak of equine encephalomyelitis. In the 1938 outbreak, a peak was reached three or four weeks after a heavy rainfall. As pre- cipitation decreased the disease diminished and, with the advent of killing frosts, disappeared. FIGURE VII RELATION OF MOSQUITO COLLECTIONS TO RAINFALL MASSACHUSETTS 1939 LEGEND number or MCSQurro collections INCHES OF RAIN 60 FIGURE VIII ACCUMULATION Of DAILY DEVIATION fROM NORMAL IN INCHES MASSACHUSETTS 1938*1939 61 Temperature During 1938, Figure XI, the temperature showed little devia- tion from normal, A deficit in Fahrenheit degree-days developed in April and remained unchanged through July, In August an excess accumulated which lasted through October, Warm weather is conducive to increased mos- quito breeding. However, the slight excess which accumulated at the end of the summer had little effect because of the lack of rainfall. DGURE IX PRECIPITATION MASSACHUSETTS 1938 & 1939 62 Again we contrast 1939 with 1938 and find that 1958 was a more favorable year for mosquitoes. The summer of 1938 was not only wetter but warmer and mosquito breeding conditions were nearer the optimum. During the 42nd week, frosts had appeared throughout central and northern Massachusetts, By the 44th week killing frosts appeared through- out most of the state except for the islands south of cape cod. No data has been collected upon the persistence of various species of mosquitoes beyond the end of October. FIGURE X RELATION Of RAINFALL TO DEATHS IN HORSES DUE TO EASTERN VARIETY OF EQUINE ENCEPHALOMYELITIS VIRUS MASSACHUSETTS I 9 3 S LEGEND DEATHS IN HORSES DUE TO EASTERN TYPE VIRUS OF EQUINE ENCEPHALOMYELITIS INCHES OF~ RAIN FIGURE XI ACCUMULATION OF DAILY DEVIATION FROM NORMAL IN FAHRENHEIT DECREED MASSACHUSETTS 1938 63 1938 K A i~\ MTL1C 64 Wind Adult mosquitoes, when borne by winds, will be disseminated over a Targe area in the direction of the wind. We determined the direction of prevailing winds for the towns in which collections were made by the Standard United States Weather Bureau Method, Table VIII lists the di- rection of the prevailing winds in the towns in which collections were made • TABLE VIII WEEK OF YEAR DIRECTION WEEK OF YEAR DIRECTION 26 SIT 35 Vf 27 SIT 36 SW 28 sw 37 SW 29 SIT 38 sw 30 SIT 39 SIT 31 W 40 NW 32 w 41 NIT 33 w 42 NIT 34 w 43 NW As the prevailing winds throughout the middle and early parts of the summer are from the west and southwest, the carrying of mosquitoes by the wind is chiefly to the north and northeast. Salt marsh mosquitoes were, therefore, carried in a northeasterly direction. In those areas of the state which arc northeast of salt water, adults of salt marsh mos- quitoes may be expected to be farther inland than where salt water is to the northeast. The dissemination of a mosquito-borne disease would bo more extensive in the direction of the prevailing winds. This observation was mo.de during the 1938 outbreak of equine encephalomyelitis. 65 CHAPTER XI MOSQUITO BREEDING PLACES Each regular collection point was surveyed as described in Chapter VI. Table IX was compiled by punch card analysis from the data recorded in these surveys. No method of selection was used in picking out the breeding placesj the crews were directed to collect samples from all the breeding places which they found, but they were not to take samples from identical sources in an area less them 100 yards in radius. There were twenty different types of breeding places included in our analysis; natural water bodies, marshes, swamps, ponds, lakes, rivers, streams and puddles were most frequent. Dumps and barrels were the two most common man-made breeding places. TABLE IX MOSQUITO BREEDING PLACES at REGULAR COLLECTION POINTS Type of No, of No, of Breeding Breeding Species Places Places Collected % of Species per Breeding Place No, of Collec- tions Average No. Collections per Breeding Place 1, Artificial Pool 46 7 .15 435 9,5 2, Barrel 82 10 .12 789 9.6 3. Bird Bath,Flower Pot 6 4 .66 63 10.5 4. Cesspool or Overflow 14 7 .50 128 9.1 5. Cistern 9 5 .5 5 62 6.9 6. Dump 92 13 .14 1,064 11.6 7. Watering Trough 27 9 .33 273 10.1 8. Cranberry Bog 88 18 .20 1,352 15.4 9. Excavation 19 11 .57 185 9.7 10. Quarry 2 5 2.50 27 13.5 11. Sand Pit 7 6 .85 47 6.7 12. Root Hole 22 9 .41 175 7.9 13. Tree Hole 15 8 .53 187 12.5 14. Well 13 11 .84 169 13.0 15. Marsh or Swamp 637 15 .024 7,781 12.2 16. Pond or Lake 468 15 .032 5,025 10.7 17. Puddle 110 14 .127 1,012 9.2 18. River or Stream 1 ,173 17 .014 10,519 9,0 19. Rocky Crevice 9 8 .88 69 7.6 20. Running and Still Water Combined 382 18 .04 3,805 9.9 Total 3,221 - —,- 9.467 33,167 204.6 = 47 10.3 66 TABLE X REGULAR COLLECTIONS OF LARVAE in DIFFERENT TYPES OF BREEDING PLACES AEDES i ! atropalpus I i icanadensis cantator jcinereus excrucians intrudens sollicitans taeniorhynchus triseriatus vexans 1. Artificial Pool - 1 1 - - - - - - - 2. Barrel - 1 19 - - 1 - 4 6 3. Bird Bath & Flower Pot - - - - - - - - - - 4. Cesspool & Overflow 1 - - - - 1 - - - - 5. Cistern 6. Dump - 1 25 1 1 1 3 - 2 12 7. Watering Trough 1 - - - - - - - 1 1 8. Cranberry Bog - 2 18 7 2 1 4 1 - 24 9. Excavation - - - - - - 1 - - - 10. Quarry 11. Sand Pit 12. Root hole 13. Tree Hole 14. Well - - - - - - - - 2 1 15. Marsh & Swamp 7 5 105 22 - - 85 - - 118 16. Pond & Lake 16 8 9 7 - - 2 - - 41 17. Puddle 1 3 11 2 - - - - - 14 18. River or Stream 26 - 1 1 - - - - - 12 19. Rocky Crevice 1 - - - - - - - - 1 20. Running & Still Water 6 44 HI - 6 «. — - 5-2 53 27 233 61 3 9 96 1 9 262 67 TABLE X REGULAR COLLECTIPEG OF LARVAE in DIFFERENT TYPES OF BREEDING PLACES cn H h-J maculipen- 03 I 03 M CD o I 1 1 1 1 ro i I-1 » 1 1 1 1 1 624 ro nis CD CD CD CO 03 ro M 03 03 00 -3 o M M M to 03 ro 03 3f* 3—1 3—1 punctipen- 5 tj CO M 03 03 CD 03 3-1 cn 03 ro CO CD CO 03 -3 CO -0 3—1 nis aj 1549 03 03 ro w cn 03 03 34 03 h-> M 03 03 10 -3 ro , -3 29 03 33 1—1 11 1 cn 37 quadrimacu- latus L385 03 ro ro -ci CO o 0*3 o CD CD 03 M ro apical is cn ro 03 -o 03 cn cn i—1 03 CD 03 3—* 03 ro 1—' ro cn cn -0 03 CO 03 CO rf»> CO CD on O 3-* cn O CD CD CD i-* CO 03 3-> ro 03 CD T 23 ro 03 ro h-> 1—1 1—1 cn Hr 3-» 8 CO 03 3-» -0 CD CD 47 59 40 >-> CO 13 71 o o -0 3-* 03 CD 24 76 36 03 cn •<1 CD pipiens ■H =J 903 105 ro 3-> CD H-* CO 03 03 03 salinarius i ■ CO* CD M CD CO M i—1 03 rf>* 03 3—1 03 3—1 CD 03 ro ' d 03 CO 03 -0 cn V-1 03 03 CD 03 ro ro 3-* 03 M1 CD 03 -3 cn -0 0*3 3—1 03 H 1 1 1 1 1 i I tcrritans 268 M 1—1 l 31 34 ro 03 1 13 26 1 1 1 11 1 1 t t 1 I I melonura S cn 1 u I i » 1 i 1 i I 1 1 1 03 1 1 1 • 1 i I morsitans b —3 > > 03 CO h-> M 3-< D »T^ I 3-* cn 03 1—* -3 cn CD CO 03 03 CO I—1 3—1 3—1 1 1 ro 03 1 1 1 1 i 1 sapphirina b Hj H > ro i—1 M M I—1 M H I—1 1—1 3—1 3—’ Column Number CD CD -0 03 cn 03 to M O CD CD -3 03 03 03 ro M 68 The number of collections averaged 10,5 per breeding place. If chance is taken adyToTS or 3,2; the chance variation of 10,3 » 2(3,2), or a range'of 3.9 to 16.7 includes all the breeding places. This indicates that the collection points were visited about the same number of times and that there is no statistical difference in the number of collections made in the different types of breeding places. This Survey, therefore, made an unselect- ed collection of larvae from the various types of breeding places. The number of species in the different types of breeding places varied from four in bird baths and flower pots to eighteen in cranberry bogs, and running and still water. Hie average number of species per brooding place is noted in Table IX, When the sum of these is divided by the number of types of breeding places, a moan of ,,47is obtained for the scries. The chance variation of this moan being 2 -VTff, the chance distribution varies from .47+* 1.4 or 1,37 to .47 - 1.4 or 0.0, This range includes all types of breeding places except one, and statistically the distribution of species in the dif- ferent types is not significant and may be due entirely to chance. TABLE XI CHARACTER OF WATER IN NATURAL HATER BODIES Type of Wat or Body Mo, of Collec- tion Points Brown Color- less Muddy Float- age Float- age & Brown Float- age & Color- less Float- age & Muddy Un- classi- fied Marsh & Swamp 637 146 179 191 22 17 19 63 Pond & Lake 468 84 271 42 - 7 24 2 38 Puddle 110 28 56 25 - 1 3 4 13 River or Strcamll73 209 653 150 1 24 27 27 102 Rocky Crovico Running & 9 - 4 3 - - - - 2 Still Water 382 58 154 36 1 4 6 12 111 TOTAL 2779 525 1297 427 2 58 77 64 329 Number of Collections Percent of Collections Marsh & Swamp 22.9 5.2 6,4 6.9 _ 0.8 0.6 0.7 2.3 Pond & Lake 16.e 3.0 9.8 1.5 - 0.3 0.9 0.1 1.4 Puddlo 4.0 1.0 1.3 0.9 - _ .1 .1 0.5 River or Stream 42.2 7.5 23.5 4.7 - 0.9 1.0 1.0 3.7 Rooky Crevice .3 - 0.1 0.1 mmm 0.1 Running & Still Water 13.8 2.1 -5.5 1.3 0.1 0.2 0.4 4.0 TOTAL ibo.o 18.9 46.7 15.4 0.0 2.1 2.8 2.3 11.8 69 This lack of significance is confirmed by the application of Student's formula for correlation. If the absolute value of r is less than 2/V n-1, then there is no significance. Hero r is calculated to bo .23 and 2/V n-1 is 2 V2CK1 which equals Z\/T§ 2/ 4.4 = ,45, Since this latter value is greater then, r, there is no statistical significance in the number of species found in any of the breeding places. The distribution of the species for each typo of brooding place is included in Table 10, It includes only collections made at regular collection points. This table includes 32,907 collections of a total of 3S,976. The importance of any typo of breeding place for each species can be determined by calculating the percent of the total which was found in tho typo under consideration. It must bo remembered that those differ- ent breeding places aro an enumeration made by the Survey and do not rep- resent a census of all such places. The conditions under which tho Survey Was made must be considered in interpreting this end all other data. The figures on larvae in this chapter apply to collections made at regular col- lection points, not to tho total collections of the Survey, TABLE XII COLLECTIONS OF VECTOR LARVAE FROM BODIES OF WATER DIFFERENT IN CHARACTER Humber of Collections AEDES ANOPHELES Character of Water ATROPAL- PUS GAITTA- TOR SOLLICI- TAI'S TASNIO- RHYNCHUS TRISERI- ATUS ■vexaTs QUADRI- MACULATUS Brown 7 28 3 - 1 50 279 Colorless 25 74 60 13 1 134 689 Muddy - 30 15 1 2 61 193 Floatage Floatage & — — — — — — Brown Floatc.go & — — - — 1 3 39 Colorless Floatc.go & 1 -k- — — — - 5 43 Muddy - 1 - - - 5 11 TOTAL 33 133 78 14 Percent of Collections 5 258 1254 Brown 21 21 4 20 19 22 Colorless 76 55 77 93 20 52 56 Iluddy - 22 19 7 40 24 16 Floatage Floatage & • * » — *" Brown Floatage & m1 20 1 3 Colorless Floatage & 3 1 *• — 2 3 Muddy - 1 - - - 2 1 TOTAL Too” 100 100 100 100 100 100 70 The breeding peculiarities of those species which are of public health importance is further analyzed in the following tables. There was a difference not only in the type of water collections in which various species breed but also in the character of the water. The nature of the water in the different types of natural water collections is analyzed in Table XI. Clear, colorless water was present in almost one-half of all collection points, brown water in about one-fifth and muddy in one-sixth. Clear streams represented ono-fourth of tho collection points. The collections of vectors of equine encephalomyelitis and of the principal carrier of malaria arc correlated with the various characteristics of the water in Table XII, Aodes cantator, Aedcs voxans, and Anopheles quadrimaculatus were collected in the different types of water as might bo cxpcctod by chance, Aedcs atropalpus, Aedcs sollicitans, and Aedcs taoniorhynchus were found in clear, colorless water more often than could be expected by chance. These three species, therefore, seem to prefer clear water to any other. A second important characteristic of breeding places is the bottom of the water collection, Tho nature of the bottom effects the chemistry of TABLE XIII CHARACTER OF BOTTOM IN NATURAL WATER BODIES Number of Collections Typo of No, of No. No, No. No. No.with No, No. Un- Natural Collec- with with with with Earth with with classi- Water Body tion earth Leaves Rocks Sand or Mud vegeta- Leave s fied Collection Points cc Mud & Rocks ' tion & Other Marsh & Swamp 63t 312 3 6 14 ll 127 152 Pond & Lake 468 208 4 4 30 36 3 71 112 Puddle 110 53 2 2 4 5 1 21 2£ River or Stream 1173 427 - 39 82 137 4 138 346 Rocky Crevice 9 1 - 2 - 1 - 2 3 Running & Still Water 382 112 2 5 14 43 3 80 120 TOTAL 2779 1113 11 58 144 257 22 439 735 Percent of Collections Marsh & Swamp 22,7 11.2 0.1 0.2 0.5 1.1 0.4 4.5 4.7 Pond & Lake is;e 7.4 0.1 0.1 1.1 1.3 0.1 2,5 4.0 Puddle 4,0 1.9 0.1 0.1 0.1 .2 0.8 0.8 River or Stream 42.3 15.4 - 1.4 3.0 4.9 0.1 5.0 12,5 Rocky Crevice 0,3 - - 0,1 - - - 0,1 0,1 Running & Still Water 13.8 4,0 0,1 0.2 0,5 1.7 0.1 2.9 4.3 TOTAL 99,7 39.9 0.4 2.1 5.2 9.2 0.7 15.8 T6.4 71 the water and also the type of vegetation that may grow in the water. This data is collected and summarized in Table XIII. Although about one-half of the collection points were characterized by clear, colorless water,the bot- toms of an equal number of water bodies were composed chiefly of earth and mud. The association of these environmental factors upon the presence of the larvae of the vectors is shown in Table XIV, There is much less asso- ciation of species and bottoms of water bodies than with species and types of water. Here, there is a wide scatter and there is no definite correla- tion in this series, except with Aedes atropalpus which prefers water bod- ies with rocky bottoms. The type of vegetation growing in the water is a third important factor in the environment of larvae .Water plants effect the chemistry of the water, afford shelter against enemies and assist in preventing rough water during windy or stormy weather. The data on the existence of various types of vegetation in the water is tabulated in Table XV, In one-third of the water bodies, the type of vegetation was not classified; in most of these in TABLE IIV COLLECTIONS OF VECTOR LARVAE FROM BODIES OF WATER WITH DIFFERENT BOTTOMS Number of Collections AEDES ANOPHELES Character ATUOPAL- 0 H > 1 S0LLICI- taMo- TRiSr&i- iMaNS qUadri- of Bottom PUS TOR TANS RHYNCHUS AT US MACULATUS Earth or Mud 7 107 39 2 1 119 691 Leaves - - - - - 2 4 Rock 11 - - - - 8 11 Sand - 8 1 - - 24 73 Earth or Mud & Rock 1 - - - - ■9 122 Vegetation - 13 40 13 - 6 3 Leaves & Other - 17 2 - 2 37 150 TOTAL 19 145 82 16 3 205 1054 Percent of Collections Earth or Mud 37 74 48 13 33 58 66 Leaves - - - - - 1 - Rock 58 - - - - 4 1 Sand - 5 1 - - 12 7 Earth or Mud & Rock 5 - - - - 4 12 Vegetation - 9 49 87 - 3 - Leaves & Other 12 2 ' - 67 18 14 TOTAL 100 100 100 100 100 100 100 72 stances, there was very little vegetation, too little to he classified as characteristic of the collection point, Lily pads were the most commonly recognized water plant, algae were the second and duclaveod third in numer- ical order. The association of larvae with these plants is given in Table XVI, As is to be expected, there is a negative correlation between lily pads and the se.lt marsh mosquitoes because lily pads seldom grow in brack- ish water, Aedcs atropalpus is associated with algae who re this plant was prominent enough to bo marked as characteristic of the collection point. This indicated that Acdcs atropalpus prefers clear, colorless water with rocky bottoms whore algae is the principal water plant. The vegetation which grows at the water edge and in shallow water is oven more important than the water plants, Harsh grass, cat-tails and other similar plants afford greater protection against rough water and TABLE XV KINDS OF VEGETATION IN NATURAL WATER BODIES Number < of Collections Typo of No. of Un- No. No, No. No# No,with No,with No,with IT at or Body Collcc- classi- with with with with Lily Algae & Duck- tion fied Lily Algae Duck- Water' Pads & Other weeds Podnts Pads weeds Mosses Other & Other Marsh & Swamp 657 163 -92 62" 26 51 135 89 20 Pond & Lake 468 90 69 20 ■6- 33 186 49 4 Puddle 110 66 1 6 6 11 5 13 2 River or Stream 1173 506 60 88 54 150 152 127 36 Rocky Crevice 9 5 1 - - 2 1 - - Running & Still Water 382 96 19 24 11 34 137 51 10 TOTAL 2779 CJ to 03 242 206 102 281 615 329 72 Percent of Collections Marsh & Swamp 22.9 5.9 3.3 2,2 .9 1.8 4.8 3.2 .7 Pond & Lake 16.8 3.4 2.5 0.9 .2 1.1 6,7 1.7 1.4 Puddle 3.9 2.4 .0 .2 .2 .4 .2 .5 .1 River or Stream 42.2 18.2 2,2 3.1 1.9 5.4 5.5 4,6 1.3 Rocky Crevice 0.3 .2 - - ~ .1 _ - Running & Still Water 13.7 3,4 .7 .9 .4 1.2 4.9 1.8 .4 TOTAL 99.8 32.4 8.7 7.3 3,6 10.0 22.1 11.8 3.9 73 against natural enemies than do water plants. Often these plants interfere with mosquito-control measures. The occurrence' of these plants in the various types of breeding places is summarized in Table XVII, Marsh grass was the most commonly recognized plant at the edges of water bodies, being almost twice as frequent as cat-tails end reeds. Other plants were observed in too small a number to justify any attempts at statistical analysis. The association of plants at the water edge and larvae is made in Table XVIII. The highest association is between Aodes taeniorhynchus and marsh grass. There is a significant association between salt marsh mosqui- toes end marsh grass, Aedes vexnns and Anopheles quadrimaculatus were col- lected with the chance frequency in association with different types of veg- etation. Lastly, not all species wore found in the same collection point. Certain species wore found in the same water collection with a greater fre- TABLE XVI COLLECTIONS OF VECTOR LARVAE FROM BODIES OF WATER WITH DIFFERENT VEGETATION Vegetation in Water ATROPAL- PUS Number of Collections CANT A- SOLLICI- TAENIO- TOH TAMS RHYNCHUS TRISERI- ATUS VEXANS ANOPHELES QUAD!? I- MACUL...TUS Lily Pads - 1 - - 1 21 63 Algae 3 46 55 15 - 18 112 Duckweeds - - - - 1 3 72 Water Mosses - 53 12 - - 23 159 Lily Pads & Other 1 5 4 14 50 440 Algae & Other 13 41 14 - 1 41 204 Duckweeds & Other 11 19 54 TOTAL 17 157 85 29 3 175 1127 Lily Pads Percent of 1 Collections 33 12 8 Algae 18 29 65 52 - 10 10 Duckweeds - - - - 33 2 6 Water Mosses - 34 14 - - 13 14 Lily Pads & Other 6 3 5 48 . 29 39 Algae & Other 76 26 16 - 34 23 18 Duckweeds & Other 7 11 5 TOTAL 100 100 100 100 100 100 100 74 quency than others. The larval associates of the vectors of equine encephal- omyelitis and of malaria are summarized in Table XIX, Aedes atropalpus was found to be most frequently associated with Culex pipiens. All other vectors were associated with Culex apicalis and Culex pipiens to about the same degree In addition. Anopheles quadrimaoulatus was equally associated with Anopheles punctipennis. It is to be noted that these associates are between species collected in a collection point one hundred yards in diameter throughout the entire season. The species may not have been collected at the same time nor from the same water collection. However, in the majority of the cases, there was only one water body at a collection point and, therefore, the associations hold as to place better than as to time. The salt marsh breeds were collected from the same water bodies as the Culex, These associations were frequently encountered among specimens contained in vials received at the laboratory. There is very little positive association between the various salt marsh mosquitoes. This observation, may be explained in part by the fact that TABLE XVII KINDS OF VEGETATION AT EDGE OF NATURAL WATER BODIES Number of Collections w W & S’ Pi g )-3 W id P3 S’ PJ o CO p o H• o P O CO p o H- o P £ ct* H* g o rr o P. P-. P P. P M t-3 > C+ H- B o f*r < o p. p. p p. p a Type of Water h-1 i—1 H- M c 9° PJ Body on o o 9° cn o o ft* p p It1 :~:4 9° P p p 9’ e p o p cp cf- < CO c*r on k* 0 H- ct o p a H* o P O o *1 o ■d P O 0 p o 2 p d I—1 o 1—1 (—1 ro t—> o • 03 • • ro • • o • ro • 03 CO h-1 -3 1—‘ (-> 03 03 03 No. of Collec- o CO 03 ro o CO CD ro CO 03 o CO ■o tions ro o o o O hi No. with Cat- • 03 • 1—' 1 • CO • h-« • • CD o p o c p 64 ro 1 ro 03 ro 12 ro cn tails & Reeds o o o O ro No. •with Pick- • • • • • o 03 ro 1 1 GO t-1 t—' ro *-+> o o t—■ 03 i—1 1 ro ro 03 cn erol .feeds i—1 • O • O • o • O • h-J e P ro No. with Arrow on ro 1 CO 1 03 ro o c+ H- O H-1 cn t ro I CD 03 Heads o o o O P M No. with 3ul- b i 1 0 • M 0 • 28 I 1 i—1 O t—1 o rushes ro CO CXI t—1 & o 03 *3 03 )—1 1—1 No, with Marsh • • • * • • CO CO CD ro | 1 -xj Grass o O 1 rf* CD ro cn ro h-1 CO CO o ro No, with Cat- cn 03 a O cn -c i-1 h-J h-> ro • • • • • • ro -o -0 ro tails. Reeds & CO ro 1 CX! CXI h-1 CD h* cn 1 CD 03 sn Other i—1 o ro -o o 03 CXI ro No, with Marsh • • • • O • 03 03 i—1 CO CD -o 1 o> ro h-1 03 03 I—1 H 03 -0 cn Grass & Other to t—> No, with Unci as- ro ro Cxi 03 03 03 • • CD • c* e ro • 03 • 03 • -a 03 H cn 03 -0 I—1 ro 03 03 CO ro O sified Vegeta- tion 75 Aedes cantator may breed in water containing less salt than that in which Aedes sollicitans breed. The fresh water Aedes vectors are significantly associated with Culex territans which v;as collected in much smaller num- bers than other species of Culex, TABLE XVIII COLLECTIONS OF VECTOR LARVAE FROM BREEDING PLACES WITH DIFFERENT VEGETATION AT WATER-EDGE Lumber of Collections ANDES ANOPHELES Vegetation at Water-Edge ATHOPAL- PUS CANTA- TOR SOLLICI- TAENIO- TANS RHYNCHUS TRISERI- ATUS VEXANS QUADRI- MACULATUS Cat-tails & Reeds . I . 9 49 Pickerel Weeds - 1 - - - 5 22 Arrow Heads - - - - - 3 27 Bulrush - - - - - 1 1 Marsh Grass 17 70 65 15 2 72 409 Cat-tails, Reeds & Other 1 52 22 2 71 378 Marsh Grass & Other 5 37 5 55 256 TOTAL 21 160 92 15 4 216 1142 Cat-tails & Reeds Percent of Collections 4 4 Pickerel Weeds - 1 - - - 2 2 Arrow Heads - - - - - n Cj 3 Bulrush - - - - - i - Marsh Grass 81 44 71 100 50 33 36 Cat-tails, Reeds’ & Other 5 32 24 50 33 33 Karsh Grass & Other 14 23 5 25 22 TOTAL 100 100 100 100 100 100 100 In all these tables only a few attempts have been made to interpret the data. Too many factors are concerned in the ecology and bionomics of mosquitoes to assign any one observation to a peculiar circumstance without due consideration of all other factors. For this reason, the observed facts have been presented without much comment so that the reader may make such interpretation as his experience and knowledge permit. 76 TABLE XIX LARVAL ASSOCIATES Humber of Collections AEDES ANOPHELES SPECIES ATROPAL- CALTA ■ ms TOR - S0LLIGI- TAIIS TRISERI ATUS - VEXA1IS QUADPlI- MACULATUS Aodos atropalpus - - - - 41 9 A.canadensis - 12 1 - 6 2 A.contator - - 50 1 80 9 A. cinercus - 15 4 - 31 10 A* excrucians - - - - 3 - A.fitchii - - - - - - A. intrude ns 1 - - - 3 - A.sollicitans - 53 - - - - A. stimulans - - - - - - A. taeniorhynchus - 15 16 - - - A.triseriatus - 1 - - 2 - A.voxans 13 45 11 2 - 70 Anopheles punctipen- nis 30 13 8 10 382 1857 A. quo.dr imaculatus 2 9 14 - 82 - Culex apicalis 34 449 123 45 1088 2394 C.pipiens 89 368 135 43 844 1837 C.salinarius r/ O 215 91 - 109 188 C.territans 47 63 15 42 438 559 Theobaldia melanura - 47 8 1 42 13 T.morsitans - - - - 1 1 TOTAL ■sit" 1335 476 142 3152 6949 Acdes atropalpus Percent of Collections 01.3 00.1 A. canadensis - 00.9 00.1 - 00.2 - A.cantator - - 10.5 00.7 02.5 00.1 A.cinoreus - 01.1 00.8 - 01.0 00.1 A.excrucians - - - - 00.1 - A.fitchii - - - - - - A.intrudens 00.5 - - - 00.1 - A.sollicitans - 06.2 - - - - A,stimulans - - - - - - A.taeniorhynchus - 01.1 03.4 - - - A.triseriatus - 00.1 - - 00.1 - A.voxans 05.9 03.4 02.3 01.4 - 01.0 Anopheles punctipen- nis 13.7 01.0 01.7 07.0 12.1 26.7 A.qu ad r imacu1atu s 00.9 00,7 02.9 - 02.6 Culex apicalis 15.5 ' 33,6 25.8 30.3 34.5 34.5 C.pipiens 40.6 27,6 28.4 30.3 26.8 26.4 C.salinarius 01.4 16.1 19.1 - 03.5 02.7 C,territans 21.5 04.7 03.2 29.6 13.9 08.0 Theobaldia melanura - 03.5 01.7 00.7 01.3 00.2 T.morsitans - - - - - - TOTAL 100*0 100.0 100.0 100.0 100.0 100.0 77 CHAPTER XII THE COLLECTION OF ADULT MOSQUITOES Adult mosquitoes were collected'by two methods. The most im- portant of these was the capture of specimens by the killing tube, which was placed directly over the resting mosquito. The second method was sweeping with nets. As the collectors were novices in using the net, and since some experience is required in its manipulation, this method was less productive than the former. There were 23,719 specimens in 8,100 collections. Adults represented 16.5% of the total collections. Although 75% or more of the adults were collected by the personnel of the Survey, and, hence, represented collections of those adults with diurnal habits, the remainder of the collections were made by volunteers and represent mosquitoes 7/ith nocturnal habits. Biting Habits This data is summarized in the following series of tables. Table XX, Adult Mosquitoes Caught on Man, is a list of those mosquitoes which were collected by placing the killing tube over a mosquito which was resting on a person's body. Although the mosquito may not have been biting, it presumably was attracted to man in the anticipation of obtaining TABLE XX ADULT MOSQUITOES CAUGHT ON MAN SPECIES NUMBER OF SPECIMENS PERCENT Aedes sollicitans 758 37.3 Mansonia perturbans 511 25.8 Aedes cantator 311 15.7 Aedes vexans 120 6.0 Aedes aurifer 52 2.6 Aedes canadensis 50 2.5 Aedes cinereus 47 . 2.4 Culex pipiens 42 2.1 Aedes excrucians 20 1.1 Aedes intrudens 19 0,9 Culex salinarius 14 0.7 Aedes taeniorhynchus 12 0.6 Culex territans 10 0,5 Anopheles punctipennis 7 0.4 Culex apicalis 6 0.3 Aedes fitchii 4 0.2 Aedes triseriatus 3 0.2 Theobaldia melanura 3 0.2 Aedes species unidentified 3 0.2 Aedes stimulans 2 0.1 Anopheles quadrimaculatus 2 0.1 Aedes dorsalis 1 0.0 1977 99.9 78 a blood meal, Aedes sollicitans is the most numerous offender. Mansonia perturbans was a ferocious biter, but, because of its early seasonal in- cidence, soon ceased to be a nuisance. Aedes sollicitans was more numerous towards the middle and end of the mosquito season. "Aedes cantator and Aedes vexans were more prevalent during the middle of the season. These last three are vectors of equine encephalomyelitis and were the three most numerous biters. There was some variation in the mosquitoes which were collected inside houses and those which were collected on man. Those which were collected inside houses were contributed by volunteers who were interested in finding out what mosquitoes interrupted their slumbers. The following table, therefore, represents mosquitoes with greater nocturnal biting habits as contrasted with those in Table XX, where diurnal activity predominated. TABLE XXI ADULT MOSQUITOES CAUGHT IN HOUSES SPECIES NULIBER OF SPECIMENS PERCENT Culex pipiens 973 31,1 Pansonia perturbans 911 29.1 Anophele s quadrirnaculatus 407 13.0 Culex apicalis 189 6.0 Culex territans 165 5.3 Culex salinarius 85 2.7 Aedes cantator 56 1.8 Aedes sollicitans 56 1.8 Anopheles punctipennis 46 1.5 Aedes vexans 44 1.4 Anopheles maculipennis 27 0.9 Culex species unidentified 26 0.8 Anopheles walkeri 23 0.7 Aedos triseriatus 19 0.6 Aedes canadensis 17 0.5 Theobaldia melanura 14 0.4 Aedes atropalpus 12 0.4 Aedos excrucians 12 0.4 Aedes aurifor 11 0.3 Aedos cinereus 10 0.3 Aedes trivittatus 9 0.3 Aedes fitchii 6 0.2 Aedos intrudcns 3 0.1 Aedes species unidentified 3 0.1 Chaoborinae species unidentified 3 0.1 Aedes stimulans 1 0.0 Aedes punctor 1 0,0 Theobaldia morsitans 1 0,0 3130 WTq Culex pipiens and Mansonia perturbans are the most frequent invaders. Anopheles quadrirnaculatus, the malaria vector, is third, Culex apicalis 79 which is described as a biter of cold-blooded animals, was fourth in this series. The Aedos mosquitoes wore infrequent invaders of hones and were not a serious menace inside buildings. This observation indicates that the greatest danger from vectors of equine encephalomyelitis is outdoors. In evaluating the data above, it is necessary to point out that all mosquitoes do not enter houses with the intent to bite. Although most mosquitoes are attracted indoors with the prospect of a blood meal, some species, such as Culex apical is enter houses to hibernate. With tho approach TABLE XXII ADULT MOSQUITOES CAUGHT ON MAN AND IN HOUSES SPECIES NTJliBER OF SPECIMENS PEPCEiJT Mansonia perturbans 1,422 27 8 Culex pipiens 1,015 19.. 8 Aedes sollicitans 794 15.5 Anopheles quadrimaculatus 409 8.0 Aedes cantator 367 7.1 Culex apicalis 195 3.8 Culex torritans 175 3.4 Aedes vexans 164 3.2 Culex salinarius 99 1.9 Aedes canadensis 67 1.3 Aedes aurifer 63 1.2 Aedes cinerous 57 1.1 Anopheles punctipennis 53 1.0 Aedes excrucians 32 0.6 Anopheles maculipennis 27 0.5 Culex species unidentified 26 0.5 Anopheles walkeri 23 0.5 Aedes triseriatus 22 0.4 Aedes intrudens 22 0.4 Theobaldia melanura 17 0.3 Aedes atropalpus 12 0.2 Aedes taeniorhynchus 12 0.2 Aedes fitchii 10 0.2 Aedes trivittatus 9 0.2 Aedes species unidentified 6 0,1 Chaoborinae species unidentified 3 0.1 Aedes stimulans 3 0.1 Aedes dorsalis 1 0.0 Aedes punctor 1 0.0 Theobaldia morsitans 1 0.0 5,107 89.4 of cold weather, mosquitoes are more likely to seek warm winter quarters, Y/hen the mosquitoes caught in houses are added to those which are caught on man, a better index of the biting mosquitoes can be obtained. This data 80 is compiled in Table XXII. Here the species are rearranged as to their numerical importance: Mansonia perturbans heads the list, Culex pipiens is second, Aedes sollicitans is third and Anopheles quadrimaculatus, fourth. Among the species captured in houses, the vectors of equine encephalomyeli- tis represent about one-fourth of the total number of specimens. TABLE XXIII ADULT MOSQUITOES CAUGHT IN BARN AND STABLE SPECIES NUMBER OF SPECIMENS PERCENT Culex pipiens 98 46.4 Mansonia perturbans 35 16.6 Aedes vexans 18 8.5 Aedes cantator 14 6.6 Culex salinarius 13 6.2 Culex apicalis 8 3.8 Anopheles quadrimaculatus 4 1.9 Culex territans 4 1.9 Culex species unidentified 4 1.9 Aedes cinereus 3 1.4 Aedes excrucians 3 1.4 Anopheles punctipennis 3 1.4 Aedes atropalpus 1 0.5 Aedes fitchii 1 0.5 Aedes sollicitans 1 0.5 Aedes stimulans 1 0,5 211 100.0 Table XXIII lists the mosquitoes caught in barns and stables. Presumably, the main attraction was the prospect of a blood meal. Here, however, the blood was not from man, but from horses, cattle and other domestic animals, A second urge which became effective with the onset of cold weather, was the seeking of a warm place in which to hibernate. Culex pipiens was by far the most frequent invader of the barn and stable. Mansonia perturbans was the second in numerical importance and iledes vexans, third, Aedes so11icitans, which is a ferocious biter of man, was caught only once inside a barn or stable. The collection of adults in relation to the density of buildings is discussed in subsequent parts of this report. Environment The collection of those species of mosquitoes which are of pub- lic health importance in different types of terrain is summarized in Table XXIV. This data is based on adults caught at regular collection points. It is to be expected that collections were made more often in certain types of ter- rain in preference to others. Cultivated fields were seldom trespassed upon and,hence,only a few collections were made here,The description of the collec- tion point area as given in this table is the chief character of the land in- cluded in the one hundred yard radius of the collection point. In many in- stances, other types of terrain were also present, but represented only a small portion of the collection point area. The totals on the left of Table XKIV furnish a base against which the species data can be compared. Aedes cantator and Aedes sollicitans were caught with about equal frequency in 81 meadows and in woods, Aedes vexans was captured most frequently in the woods. The preference of this mosquito for the woods is an important factor in any control-program that may be instituted against equine encephalomyeli- tis, Horses should be removed from pastures that are in close proximity to TABLE XXIV ASSOCIATION OF VECTOR ADULTS WITH DIFFERENT TYPES OF TERRAIN Number of Collections 1 I AEDES ANOPHELES TOTALS Nature of terrain atropalpus o -p d -P g o sollicitans i u o •H CO d g o X d o -P 1 1 triseriatus ; voxans quadrimacu- latus totals Cultivated Fields - 7 10 - - 7 3 27 Me ad ow-Pastured - 11 32 1 4 1 2 51 He ad ow-Unpas tu red - 102 177 8 2 16 10 315 Rocky - - - - - 1 Kj 4 Woods - 67 92 3 16 56 14 248 Meadow & Woods - 70 99 1 5 24 5 204 Meadows & Cultivated Fields 1 11 20 - 2 4 2 40 TOTAL 1 268 430 13 29 109 39 889 Percent of Collections Cultivated Fields - XT' "■r.B - - 6.4 7.7 3.0 Me ad ow-Pastured - 4.1 7.4 7.7 13.8 0.-9 5.1 5.7 Lie ad ow-Unp as tu r ed 33.1 41.1 61.5 CO • CD 14.6 25.6 35.5 Rocky - - - - - .9 7.7 .4 Woods 25.0 21.3 23.1 55.5 51,3 35.9 27.9 Meadow & Woods 26.1 23.1 7.7 17.2 22.0 12.8 23.0 Meadows & Cul- tivated Fields 100.0 4.1 4.6 - 6.8 5,7 5.1 4.5 TOTAL 100.0 100.0 100.0 100,0 100.0 100.0 100.0 100.0 woods, and people should refrain from entering woods during outbreaks of this disease. In this way, exposure to Aedes vexans which may be infectious will be greatly reduced. If we could apply the data collected by this vey, it seems apparent that one-half of the exposures to Aedes vexans would be eliminated simply by keeping away from woods. These facts seem to apply to Aedes triseriatus and Anopheles quadrimaculatus, the principal vector of ma1aria; however, the number of collections in both those instances is smaller and statistically this conclusion is less certain. Aedes atropalpus and Aedes taeniorhynchus were captured in too small a number to permit any significant inference. In Table XXV the association is made of vectors to various typos 82 of trees. Here again it must be remembered that the data is based on col- lections from regular collection points, and that the trees described were the predominating type in the collection point area one hundred yards in radius. Hardwoods are much more numerous in Massachusetts than any other type of tree. In estimating the significance'of any association, the total collections must,therefore,bo used as a base,There appears to be no other association than a chance distribution in all instances except on that of Aedes vexans and mixed trees where more adults were captured than might be TABLE XXV ASSOCIATION OF VECTOR ADULTS WITH DIFFERENT TYPES OF TREES Humber of Collections AEDES J ANOPHELES TOTALS TREES atropalpus cantator .sollicitans taeniorhynchus triseriatus Vexans quadrimacula- tus totals i Evergreen - 7 16 - - 1 - 24 Hardwood 2 151 254 14 12 28 25 486 ITillow - 4 7 _ 9 * 13 Fallen Trees - - - _ _ 2 2 Burned Trees - - - - - - - Evergreen & Hardwood 1 85 108 - 11 88 10 303 Fallen Trees & Ev- ergreen or Hardwood 32 64 40 12 13 -9 170 TOTAL 3 279 449 54 35 132 46 998 Percent of Collections Evergreen *w 2.5 3.5 > .8 ' - 2.4 Hardwood 66*6 54.1 56.5 25 .9 34 .2 21.2 54 .3 48,7 W i 11 ow - 1.4 1.5 - - 1 .5 _ 1.3 Fallen Trees - - - - _ — 4 .3 .2 Burned Trees - _ — _ Evergreen & Hardwood 33,3 30.4 24,1 31 .4 66,6 21 .7 30.4 Fallen Trees & Ev- ergreen or Hardwood - vH ■ • I 1 rH 14.2 74 .1 34 .2 r .8 19 .5 17,1 TOTAL 99.9 99.8 99.8 100 .0 99 .8 99 .9 99 .8 100,1 expected by chance. This may indicate that in general there is no associa- tion between any type of trees and any of the vectors. The unexpectedly largo number of adults of Aedes voxans captured in mixed Y/oods is difficult to explain as specimens were captured in smaller numbers among hardwood and also evergreen trees,The numbers, however, are too small to be conclusive. 83 CHAPTER XIII VECTORS OF EQUJI1E ENCEEHALOKYELITIS Numerical Importance of Vectors There ai-e six mosquitoes in Massachusetts which.'have been demonstrated in the laboratory to transmit the eastern virus. These are all Aedes mosquitoes. Their numerical importance in relation to other species, both vectors and non-vectors, is discussed in this chapter. The geographical and seasonal distribution, the life habits and public health importance of such species is discussed in Chapter XV, TABLE XXVI NUMERICAL IMPORTANCE OF VECTORS OF EQUINE EMCEEUAL0MY3LITIS SPECIES LA Number ' EY' SPL RVAE —f OIMENS Number ADULT IT Speci- mens Numerical Importance in % Aedes atropalpus 993 94.3 60 5.7 1,053 7.8 A, cantator 2,704 67.0 1,329 33.0 4,033 29.7 A, sollicitans 1,054 29.3 2,548 70.7 3,602 26.6 A. taeniorhynchus 112 84.8 20 15.2 132 1.0 A, triseriatus 92 29.7 228 71.3 320 2.4 A* vexans 3,358 76.0 1,052. 24.0 4,410 32.5 TOTAL S",3l3 61.3 5,237 3ST7 13,550 100.b In Table XXVI the vectors are evaluated on the basis of the num- ber of specimens collected, A. vexans is the most numerous, A. car.tator and A, sollicitans are second and third respectively, in numerical impor- tance. The other three vectors are far below these in numbers. The per- cent of adult specimens was highest in A. sollicitans and in A. triseria- tus; the latter, however, was caught in much smaller numbers. TABLE XXVII NUMERICAL IMPORTANCE OF VECTORS OF EQUINE ENCEPHALOMYELITIS ~~ BY CQlIEcTlCNS ’ SPECIES LARVAE Number % ADULT Number % Total Collec- tions Numerical Importance in % Aedes atropalpus 77 65*3 41 34.7 118 3.5 A, cantator 399 40,0 600 60.0 999 30.6 A, sollicitans 145 15.3 802 84,7 947 29.0 A. taeniorhynchus 17 48.5 18 51.5 35 1.1 A, triseriatus 33 17.3 158 82.7 191 5.9 A, vexans 519 53,3 454 46.7 973 29.8 TOTAL 1,190 36.5 2,073 63.5 3,262. 100.0 84 When the numerical importance of the vectors is evaluated on the number of collections, there is a slight but unimportant rearrangement in this series. In Table XXVII this evaluation is made. A, cantator was TABLE XXVIII NUMBER OF SPECIMENS PER COLLECTION VECTORS OF EQUINE ENCEPHALOMYELITIS SPECIES LARVAE ADULTS Aedes atropalpus 12,9 1.5 A. cantator 6,8 2,2 A, sollicitans 7 .-3 3,2 A, taeniorhynchus 6,6 1.1 A, triseriatus 2.8 1.4 A, vexans 6.5 2.3 All vectors 7.0 2.5 collected most often; A. vexans and A. sollicitans were second and third in this series. However, there is no statistical significant difference in either evaluation of the importance of these species, and it may be concluded that these vectors were collected with about the same frequency and are, probably, of about the same numerical importance. In this evalu- ation, the percent of adult collections is much higher. Whereas only TABLE XXIX VECTORS OF EQUINE ENCEPHALOMYELITIS PERCENT OF COLLECTIONS OF LARVAE WHICH WERE VECTORS Aedes County at ropalpus o -p ai -P § o sollicitans taeniorhyn- chus triseriatus w CD t> vectors “ Percent of •g collections which were w vectors i—1 i—i Cj Barnstable 0 184 48 0 0 167 309 2870 13.9 Berkshire 0 0 0 0 2 59 61 4507 1.4 Bristol 0 39 2 0 2 21 64 1931 3.3 Dukes and Nantucket 0 112 70 17 0 30 229 1563 14.7 Essex 3 11 3 0 0 11 28 3711 .15 Franklin 29 0 0 0 2 24 55 2507 2.2 Hampden 35 0 0 0 7 40 82 3193 2.6 Hampshire 10 0 0 0 1 39 50 1543 3.2 Middlesex 0 12 4 0 1 17 34 6278 .5 Norfolk 0 6 3 0 9 7 25 2514 1.0 Plymouth 0 28 14 0 3 60 105 4043 2.6 Suffolk 0 7 1 0 0 2 10 388 2.6 Worcester 0 0 0 0 6 42 48 5935 ©8 77 399 145 17 35 519 1190 40983 2.9 85 MAP II MASSACHUSETTS DEPT OP PUBLIC HEALTH DISTRIBUTION OF PROVED EXPERIMENTAL VECTORS OF EQUINE ENCEPHALOMYELITIS EASTERN TYPE salt MARSH LEGEND FRESH WATER 5 AE0E5 SOLLICITANS V ALOES VEXANS C AEDES CANTATOR T A E OES T R IS ER I AT U 5 N AEDE5 TA £ N IORMYNCHUS A AE DES ATROPALPUS 86 38,7/o of the specimens were adults, 63,5/£ of the collections were adults. This difference indicates that the average number of specimens per collec- tion was greater for larvae than for adults. In Table XXIX the average number of specimens of larvae and adults of each species is listed. The average of the larvae per collection was seven which is almost three times the average of the adults. There is no significant statistical difference in the number of specimens per collection, either among the adults or the larvae. The large number of larvae of A. atropalpus, however suggests that large broods were found in one place. Adults of the three more numerous vectors, A. sollicitans. A, vexans and A. cantator, were cap- tured in slightly larger collections than the other vectors. This differ- ence is probably due to the fact that there were more specimens of these species• The number of vectors collected varied from one section of the state to another. Collections of larvae are tabulated by counties in Table XXX, A, atropalpus larvae were collected in four counties, three in the Connecticut River Valley and one in the northeastern part of the state, A. cantator and A, sollicitans larvae were collected only in the counties along the coast and A, taeniorhynchus only in Dukes County, A. triseriatus was collected in small numbers in most of the counties, A, voxans: was the most numerous species and was collected in all counties. Of the larvae collected in Dukes, Nantucket and Barnstable Counties, Ql% wore vectors. Equine encephalomyelitis, however, has not been reported from this area. In the remainder of the counties, there was no statisti- cal difference in the percent of larvae which wore vectors. TABLE XXX VECTORS OF EQUINE ENCEPHALOMYELITIS PERCENT OF COLLECTIONS OF ADULTS WHICH WERE VECTORS Aedos County co p Pa p w § ■p co co P -P d CO o •H o Percent of collections r-H a o -p •H O i 3 OX •H P CO CO p 0 Pa which were Pa o d -P •H i—1 •H O p a o co § o -p CO vectors p P rH o Fs •H K o 1—1 -p d O drd p > . Barnstable 6 163 196 0 6 126 497 1395 35.6 Berkshire 0 0 0 0 12 12 24 4 7T .5 Bristol 0 14 7 0 2 35 58 206 28.2 Dukes and Nantucket 0 168 290 17 3 31 509 625 81.4 Essex -2- 129 206 0 14 31 382 989 38.7 Franklin 26 0 0 0 33 21 80 424 18.9 Hampden 4 0 0 0 13 23- 40 213 18.8 Hampshire 1 0 0 0 9 6 16 85 18.6 Middlesex 1 4 16 0 8 27 56 1217 4.6 Norfolk 0 14 30 0 13 26 83 464 17.9 Plymouth 100 46 1 4 60 211 823 25.2 Suffolk 0 7 10 0 6 8 3i 158 19.6 Worcester 1 0 1 0 36 48 86 1024 8.4 41 599 00% 18 159 454 2073 8100 25.6 87 The percent of adult collections which were vectors varied from county to county. Table XXXI summarizes this data. A. atropalpus adults were collected in small numbers in the Connecticut River Valley and in northeastern Massachusetts, and on Cape Cod, A, cantator and A. solliici- tans adults were collected in the coastal regions and, occasionally, further inland. A. triseriatus and A. vexans adults were captured in all counties, the latter being found in far greater numbers. In Dukes and Nantucket Counties 81% of the adult collections were vectors. This figure is much higher than elsewhere in the state. In Essex and Barnstable Counties, the vectors represented 39% and 36$ respectively, Bristol County vectors made up 28$ of the adult collections. Vectors comprised 18$ to 19$ in Franklin, Hampden, Hampshire, Norfolk and Suffolk Counties, In Berkshire, Middlesex and Worcester Counties, vectors comprised 0,5%, 4,6$ and 8,4$ respectively, a statistical significant difference. Collections of adult vectors comprised 25,6% of the total adult collections in the Survey, Adult specimens of vectors were 22,1$ of the total. This indicates that collections of adult vectors wore composed of a smaller number of specimens than those of other species. Consequently, when the relative density of adult vectors is determined on the basis of specimens collected, the percent of vectors becomes smaller. Vectors com- prised 76% of the adult specimens from Dukes and Nantucket Counties, again the highest figure for the state, Essex, Barnstable and Norfolk vectors TABLE XXXI VECTORS OF EQUINE ENCEPHALOMYELITIS PERCENT OF ADULT SPECIMENS WHICH WERE VECTORS ADULT SPECIMENS CO £ 1—1 cJ p< o u -p at Acdos Percent of collections which were vectors cantator sollicitans taenio- rhynchus triseriatus SITCXGA vectors All species Barnstable 12 439 823 0 T 413 1694 6089 27.8 Berkshire 0 0 0 0 39 15 54 1395 3.9 Bristol 0 33 8 0 2 54 97 638 15.2 Dukes and Nantucket 0 36-7 750 19 3 61 1180 1549 76.2 Essex 2 206 648 0 15 48 919 3010 30.5 Franklin 35 0 0 0 40 35 110 616 17.9 Hampden 5 0 0 0 19 47 71 407 17.4 Hampshire 4 O 0 0 9 7 20 209 9.6 Middlesex 1 6 82 0 9 95 193 3272 5.9 Norfolk 0 86 136 0 21 46 289 1330 21.6 Plymouth 0 175 86 1 4 134 400 2476 16.2 Suffolk 0 14 34 0 10 9 67 583 11.5 Worccster 1 O 1 0 50 88 140 2130 6.6 60 1326 2548 20 228 1052 5234 23710 22.1 88 MAP ill MAIN DRAINAGE AREAS OF MASSACHUSETTS 89 ranged from 30$ to 21$, Bristol, Franklin, Hampden, Plymouth and Suffolk Counties ranged from 20$ to 11$, In Berkshire, Hampshire, Middlesex and Worcester Counties, vectors comprised less than 10$ of the adult specimens* Biting Habits Table XX listed the adult mosquitoes captured on man. The vectors were represented as follows: PERCENT NUMBER Aedes sollicitans 37.3 738 A, cantator 15.7 311 A* vexans 6.0 120 A, taeniorhynchus 0.7 12 A, triseriatus 0.2 3 A, atropalpus 0.0 0 59.9^ 1184 Table XXI lists the adult mosquitoes caught in houses. Here the vectors were represented as follows: PERCENT NUMBER Aedes cantator 1.8 &6- A, sollicitans 1.8 56 A. vexans 1.4 44 A, triseriatus 0.6 19 A, atropalpus 0.4 12 A, taeniorhynchus 0.0 0 6.0% w Of the 1977 adults captured on man, 1184 or 59,9/o were vectors. Of the 3130 adults caught in houses only 187 or 6,0/£ were vectors. It had already been pointed out that the vast majority of the mosquitoes captured on man were collected outdoors. Therefore, it is at once apparent that the chances of a vector biting man are about ton times as great outdoors as indoors. This information is important in protecting animals and man from unnecessary exposure to vectors during outbreaks of the disease. Measures should be di~ rected toward the removal of horses and mules from pastures and into screened stables. Children and infants, as well as adults, should be kept behind screens as much as possible and not permitted to remain unprotected when outdoors where mosquitoes are prevalent. Unfortunately, the collections of mosquitoes on animals were so small that they are of no value. The two hundred eleven specimens which were captured in barns and stables may bo an indication of the attraction of the vectors to horses and cattle. There were 33 vectors captured in barns; these were A, vexans 18, A. cantator 14, A. sollicitans 1, forming 8,5$, 6,6$, 0.5$ of all mosquitoes captured in these buildings. These numbers are too small to be conclusive. If the situation is analogous to man, then wo may assume that whereas only 15,5$ of the mosquitoes captured in barns and stables were vectors, the vectors comprise a much larger per- cent of the mosquitoes which bite animals outdoors. Distribution by Watersheds The distribution of vectors according to water- sheds has been determined by punch card analysis. The watersheds are noted on Map III. Towns had to be considered as units and were placed into that watershed into which most of the town drained. This distribution is listed 90 TABLE XXXII VECTORS OF EQUINE ENCEPHALOMYELITIS DISTRIBUTION DRAINAGE AREAS NUMBER OF COLLECTIONS * DRAINAGE AREA i atropalpus Aedes co I U -P O *H -P O cj *H -P i—1 d i—1 d O o w taenio- rhynchus triseriatus vexans All Vectors Salt V/ater Cape Cod 6 297 264 0 5 294 8 66 Cent.Coastal 9 ' 46 70 0 8 19 152. East Coastal 0 21 T9 0 1 31 72 Ipswich 12 121 245 0 14 4? 434 Islands 0 267 367 37 3 68 742 So.Coastal 0 147 43 1 ■5 110 306 27 899 1008 38 36 564 2572 Boston Harbor 0 0 0 0 28 44 72 Merrimac 0 0 0 0 19 69 88 Rhode Island West 1 0 0 0 17 56 74 East 0 12 9 0 5 44 70 Total 1 12 9 0 22 100 144 Connecticut 117 0 0 0 77 335 529 Berkshire 0 0 0 0 14 86 100 Grand Total 145 911 1017 38 196 1198 5505 * Interpolated from punch card analysis. in Table XXXII. The highest numbers of vectors were collected in the "Islands" and "Cape Cod" watersheds. Because three of the vectors are salt marsh mosquitoes, it is only natural that the coastal salt water areas, as a whole, have more vectors than other watersheds, The "Berk- shire" and "Merrimac" watersheds have a low percent of vectors, although mosquitoes are not significantly less prevalent. 91 CHAPTER XIV VECTORS OF MALARIA Numerical Importance All of the Anopheles of Massachusetts may act as vectors of malaria. However, A. quadrimaculatus is the only important one. A. maculipennis may transmit the plasmodia with greater effective- ness than A. punctipennis, but the latter is much more numerous and henco may play a greater role. A. crucians and A. walkeri are rare and hence are of no importance. The collection data on these vectors is summarized in Table XXXIII. The Anopheles comprised 19,3% of the total TABLE XXXIII VECTORS OF MALARIA DISTRIBUTION OF SPECIES AND COUNTIES County ANOPHELES cru- c i ans j r i •H H 2 o (J 6 pennis [ puncti- pennis { quadri- « to 2 2 o -P d cj P rH I walkcri Total A L A L A L A T iJ A L A L Barnstable 5 0 0 O ✓ 41 4 21 1 7 67 Berkshire 0 11 42 830 29 57 1 8 72 906 Bristol 1 2 12 244 11 152 1 2 25 400 Dukes and Nantucket 0 0 0 5 0 0 0 5 Essex 1 o 1 15 292 60 619 12 6 89 919 Franklin 4 15 544 2 23 0 1 18 577 Hampden 5 21 1 543 4 1S9 0 4 25 1541 Hampshire 2 3 146 O' 9 1 8 158 • Middlesex 4 22 443 14 178 3 36 632 Norfolk 2 2 29 20 117 2 o c 24 250 Plymouth 1 5 5 592 14 241 4 23 640 Suffolk o 3 1 2 3 5 Worcester 2 21 50 1 341 18 116 7 4 77 1482 TOTAL 0 7 6 58 192 5757 182 1729 28 31 407 7989 collections; 22,1% of the larvae and 9,4% of the adults. The largest numbers of collections of Anopheles, 1541 end 1482, were made, respectively, in Hampden and Worcester. Since Worcester is much larger than Hampden, the Anopheles were more prevalent in the latter county. Very few collec- tions were made in Dukes, Nantucket, and Suffolk Counties. The small number found in Suffolk County is easily explained because this county comprises the City of Boston and several other densely populated communi- ties whore mosquitoes are less likely to breed, Dukes and Nantucket Counties, on the other hand, are quite rural and why Anopheles were collect- ed in such small numbers has not been explained. 92 Q. ANOPHELES QUADRJMACULATU5 P ANOPHELES P UNCT IP ENNI5 M. ANOPHELES MACULIPENNIS W ANOPHELES WALKERI C. ANOPHELES CRUCIANS ILL? IV MASSACHUSETTS DEPT. OF PUBLIC HEALTH VECTORS OF MALARIA legend * 93 .Biting Habits Anopheles were rarely captured on man outdoors. There were only 7 A, punctipennis and 2 A, quadrimaculatus among a total of 1977 mosquitoes captured”on man. It seems that these species are not serious offenders in the open# Of 3130 mosquitoes captured in houses, A. quadrimaculatus comprised 13,0$, A. punctipennis 1,5$, A. maculipennis 0,9$ and A. walker*! 0«7$j a total of 16,1$, Anopheles apparently prefer to bite man indoors. This observation may be contrasted with the Aedes vectors of equine encephalomyelitis where the situation is reversed. Of a total of 211 mosquitoes captured in barns and stables, 7 specimens (3,3$) TABLE XXXIV VECTORS OF MALARIA DISTRIBUTION IN DRAINAGE AREAS BY COLLECTIONS* ANOHiELh Is V,rat or shed crucians maculipennis punctipennis w 3 1 -P •H cj k rH *3 3 CS O 3 d e walkeri Total Salt Water Capo Cod 5 1 46 5 1 5-8- Central Coast 0 1 7& 145 0 226 East Coast 1 1 146 152 0 300 Ipswich 1 2 331 535 30 Q99 Islands 1 ■5 0 0 6 South Coast 1 196 132 1 330 TOTAL 7 1003 970 32 2019 Boston Harbor 0 5 293 202 6 505 Merrimac 0 7 803 232 9 1051 Rhode Island West 0 3 427 53 5 488 East 0 8 354 202 14 5-76 TOTAL^ 0 11 781 255 19 1066 Connecticut 0 28 2732 303 13 3076 Berkshire 0 7 704 81 9 801 GRAND TOTAL 7 65 6316 2043 88 8519 * Interpolated from punch card analysis. were Anopheles« Collections of mosquitoes on animals wore not attempted. It is, therefore, impossible to say that Anopheles are not attracted to 94 animals, but the larger proportion of specimens captured in houses in- dicate that Anopheles prefer to bite man. The detailed analysis of each species of Anopheles is included in Chapter XV, Distribution by Drainage Areas The most noteworthy observation in this distribution is the fact that Anopheles arc more numerous along large rivers. The main Connecticut River Valley is the best illustration of this distribution. Collections were most numerous in towns adjacent to the river, and least numerous in towns furthest from it. This peculiar distribution is due to the breeding habits of this genus since it pre- fers the rivers and streams to all other places, (See Table X, page 66) The distribution of Anopheles by drainage areas is summarized in Table XXXIV. 95 CHAPTER XV MOSQUITOES OF MASSACHUSETTS Genera The order of Diptera is subdivided into a number of families; the particular family of flies to which all mosquitoes belong is termed Culicidae. This family is composed of two subfamilies, the Culicinae and the Chaoborinae. The members of the first subfamily are readily distinguished from the other by the presence in the female of a con- spicuous proboscis adapted for bloodsucking. The Culicinae, or biting mosquitoes, arc divided into two tribes, the Anophelini and the Culicini. The tribes,in turn, are divided into genera, and genera into species. The tribe, Anophelini, contains only one genus, the Anopheles. All the other genera of biting mosquitoes belong to the tribe, Culicini. The name of a mosquito, as it is generally used, consists of the name of the genus and that of the spocics. TABLE XXXV RELATIVE IMPORTANCE OF TEE GENERA OF MASSACHUSETTS MOSQUITOES PERCENT OP ADULTS AND LARVAE BY SPECIMENS Total Relative Genus Larvae Adults Sped- Importance Number /« Number % mens ysr.% Aedes 9,944 &4*Y 8, #21 45.3 18,165 6,5 Anopheles 31,690 96.2 1,250 3.8 32,940 11.8 Culex 208,099 86.5 7,546 3.5 215,645 77.4 Mansonia oo C/3 ro 1“ ro i CD n 03 I—1 1—1 ro ro 1 ro colP fitchii to CO ro ro ro 03 03 ro 03 ro ro CO h-1 in !> i co l-J ro salinarius cn » i i i i t I i i 1 1 I cn i 03 03 cn -o o 03 03 cn -3 03 CO ro -o to cn Oi -o CO -o cn ro ro ** I i | h-* !—1 1 1 * i 1 1 | ro hirsuteron I 03 h-1 in I • I i—1 1 » 1 1 i ro 1 i I—' tr* i co -0 i—* ro o 03 ro h-* -^3 1 CO ro Cn CD cn 03 CO 1—1 CO O 03 o> 03 r-, r / s i—1 03 j 03 i-r- i—1 terntans / !sj 03 M k-1 1 ; 1 1 h-j i 1 i -o P implacabilis cn i—1 cn ro ro M lo hfr i—1 t-> CO P » CO -o 03 03 CD O o CD 03 CD / o 03 t—1 i—1 1 ; i 1 1 h—1 i 1 i ! i 03 03 i—1 03 03 o cn CD h-> CO CO Olt-* / B » i 1—1 ■»... p 1—1 i 03 M ro t—1 ro 031 03 1- ro M 03 i ro tn 1—* ro h^. l~> i-j O 03 ro 03 03 M CD ro ro 03 -0 co CXI ro H 1 C*3 1 -1 intrudens O 03 03 in 03 I-* ro CO i—1 CO P cn in A 7 ■per turbans i 03 . OD ro i s h-1 1 1 1 ro 1 1 ( 1 03 tH 1 03 CO ro 1 M in I i h-1 i 1 1 i I Hh P i . _ -3 CJIi 1 i i—1 I 1 1 1 i 1 1 1 1 punctor • i L 1 l I i I 1 1 1 i ■I 1 1 1 H i * I 1 I I i ro i—1 1 M i I r. ciliata § ro I 1 1 I 1 ro i i 1 1 i 1 i O CO ro ro t-1 i - P) ■■ o. i—1 in 03 I-1 03 co cO 5 p O 03 o 03 I 1 i O O -] 1 03 hi i « i 1 1 I 1 i l ( 1 1 « 1 columbiae fcj H sollicitann » i i I I i 1 ro m i 1 1 ! 1 i h-H a- i§> Cjv i 14 n in | | CO 7 0 ro rnfc—i pi ro j-j 1 1 l « i i i M 1 » ? i r ♦ h ! irroatiens jj-'i 03 M i i 1 1 I 1 1 1 i I 1 1 1 | 1 *3 COj in i—1 •n « M t-1 I-1 on i—r 1 1 CD stimulans col !0 ro i 1 i » 1 | | i f i 1 1 ro ir* ! 03 ro 1 1 i 1 r-> ! i 1 1 1 1 | td * inornata P I I i 1 1 l 1 I \ I 1 1 1 1 •r b cr ' i H i > 1 ' i I ■3 1 1 ' r taeniorhyn- 1 CO Jh-1 1 ’! 1 -» chus ro P 1—1 -o cn CD I ro in on H* 1 1 03 > r* I i « i r 1 I i I 1 1 » ro melanura / j 03 cn M 1—1 Cn O 12 cn I in i—1 h-1 P O 1 SUl i ‘ o: *-> I rol i i i I—1 H i « I I 1 1 M i i i i 1 I 1 I 1 1 T i b trichurus i i 03 i 1 ro i i I i « 03 I 1 3-1 morsitans i-j I 1—1 on 03 i—1 1—1 03 i—1 t—1 j -o (—■ 1 ro i—1 03 i i I h-1 ro j 1 t! COI 03 0-1 n 03 03 CO 03 03 in 03 ro to 03 " • . tnseriatus 03 3> 03 03 t 03 CD h-1 H -0 ro i t ro ro » L- i 12 03 1 ro i cn i i i l I , I—1 M >1 k » j 03 H* sauphirina el 03 I—1 M 1 hJ 1 1 1 1 i 1 I i i trivittatus » to cn -o 03 ro 03 03 cn in 03 if* § 1 1 ! f r J 1 h-1 1 1 i I ! tr* t i 03 -o 1 03 o o o 03 03 h-1 ro CO CO 1 p* hC=. cn 03 ro ro ro ro 03 03 ro i ; CO CO o cn o 03 03 i—* H-1 1-3 on r3 03 P H-J i 1 i i i 1 1 | • | | (—■ I p vexaiis M smith! 1 I! &• in 03 h-1 03 t> ro M 03 ro cn 5b 1 • 1 ro ' 1 i 1 i 1 t \ 1 l I 1 ro y CD! W ro o -o CO o in M o M1 CD i p 104 TABLE XL A SEASONAL DISTRIBUTION BY iTEEKS Number of Collections Larvae Week of Year 27 28 29 30 31 52 35 Total Collections 296 53 2 394 515 460 553 585 Aedes atropalpus 0 2 4 0 6 6 9 A. aurifer 0 0 0 0 0 0 0 A„ canadensis 4 0 1 2 1 4 0 Ac. cant at or 16 3 16 20 16 5 15 A, cinereus 8 2 1 2 2 4 0 A. dorsalis 1 0 0 1 1 1 9 A, excrucians 0 0 0 1 1 0 0 Ac fitchii 1 0 0 0 0 0 1 A0 hirsuteron 0 0 0 0 0 0 0 Ac implacabilis 0 0 0 0 0 1 1 A, intrudens 0 0 1 0 0 3 0 A, punctor 0 0 0 0 0 0 0 A, sollicitans 2 0 12 12 9 2 1 A* stimulans 0 0 0 0 0 0 0 A, taeniorhynchus 0 0 1 0 0 0 0 A* trichurus 0 0 0 0 0 0 0 A. triseriatus 1 0 4 1 0 9 6 A, trlvittatus 0 0 0 0 0 0 0 Ac vexans 17 6 18 4 13 60 24 Anopheles crucians 0 0 0 0 0 0 0 A. maculipennis 0 0 1 1 4 6 7 A* punctipennis 12 37 78 106 84 260 347 A, quadrimaculatus 4 2 4 4 27 58 132 A, walkeri 0 0 0 0 ' 2 9 3 Gulex aoicalis 92 208 ,390 480 656 824 930 C, pipiens 47 72 146 195 313 465 451 C, salinarius 7 11 22 11 22 31 20 C, territans 29 47 88 120 150 165 193 Mansonia perturbans 1 3 0 1 4 2 2 Psorophora ciliata 0 0 0 0 0 0 1 P. colunbiae 0 0 1 0 0 0 0 Theobaldia impatiens 0 0 0 0 0 0 0 T, in o mat a 0 0 0 0 0 ' 0 0 T, melanura 2 1 5 13 19 14 13 T, morsitans 1 2 1 0 1 0 0 Uranotaenia sapphirina 0 12 30 39 66 105 102 'vTyeomyia smith! i 0 0 0 0 0 0 0 TABLE XL A SEASONAL DISTRIBUTION BY WEEKS Number of Collections Larvae 34 35 36 37 38 39 40 41 42 43 548 353 381 588 902 839 608 365 126 42 9 9 10 12 5 5 5 4 0 0 0 0 0 0 0 0 - 0 0 0 0 3 0 8 4 0 3 1 8 3 0 18 14 93 73 42 22 13 5 7 3 2 6 43 12 5 4 2 1 0 0 0 0 0 0 3 0 0 0 0 0 2 1 1 0 0 0 1 0 1 0 0 0 0 0 0 0 • 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 21 5 46 18 7 1 0 2 1 1 0 0 0 1 0 0 0 0 0 0 8 0 7 0 0 0 0 1 0 0 0 1 1 0 0 0 0 0 0 0 4 3 0 1 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 89 35 220 58 12 2 17 19 4 0 0 0 1 0 0 3 0 1 0 0 8 4 10 6 4 3 3 1 . 0 0 446 577 577 683 742 67-7 659 378 171 32 172 188 226 224 244 256 197 114 19 5 3 3 0 3 5 1 1 3 1 1 1095 1314 1245 1307 1265 1140 1164 631 339 51 659 853 913 1067 1225 1526 1702 983 672 246 24 33 47 90 70 126 169 86 62 27 286 259 214 286 323 477 509 230 220 41 4 0 0 1 0 2 3 12 15 22 1 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 11 14 12 10 13 32 56 22 27 9 0 0 1 3 0 1 1 0 0 0 84 84 75 82 43 16 18 2 1 0 0 0 1 0 0 0 • 0 0 0 1 106 TABLE XL B SEASONAL DISTRIB1JTIOIT BY VfEEKS /£of Total Collections Larvae Week of fear 27 28 29 30 51 32 33 Total Collections 286 512 394 515 460 553 . 585 Aedes atropalpus 0,0 0.5 0.5 0.0 0o4 0,3 0.2 A, aurifer 0.0 0,0 0.0 0,0 oa 0.0 OcO A, canadensis 0 09 0,0 0.1 0.1 oa 0 02 OoO A, cantator 6 A 0.7 2,0 2,0 ia 0,2 Oc 6 A, cincreus 3.2 0,5 0.1 0.2 0,2 0,2 0,0 A, dorsalis 0.5 0.0 0.0 0,1 0.07 0.05 0.39 A, excrucians 0.0 0.0 OcO 0,1 0.07 0.0 C .0 A 3 fitchii 0.4 0,0 0.0 0,0 0,0 0,0 oa A, hirsuteron 0.0 0,0 0.0 OcO oa 0,0 0.0 A, implacabilis 0.0 0*0 0.0 0.0 OoO 0.05 0,04 A, intrudens 0,0 0,0 Ool 0.0 0,0 0,1 0,0 A. punctor 0,0 0,0 0,0 0.0 0,0 0.0 0,0 A, sollicitans 0.8 0.0 1.5 1.2 0.6 0.1 oa A, stinulans 0.0 0,0 0.0 OoO 0.0 0.0 0.0 A& taeniorhynchus 0.0 0.0 0.1 OcO 0.0 0,0 0,0 A, trichurus 0.0 0,0 0.0 0,0 0,0 0.0 0,0 A, triseriatus 0,4 0.0 0,5 0,1 0.0 0.4 0,3 A* trivittatus 0,0 0.0 OoO 0,0 0,0 0,0 0,0 A0 Texans 6,8 1.4 2,2 0,4 0,9 2,9 1,0 Anopheles crucians 0.0 0.0 0.0 0.0 0.0 0,0 0,0 A, maculipennis 0,0 0,0 0.1 oa 0.3 0o3 0.3 A, punctipennis 4.8 8,4 9,7 10.5 5.7 12.4 14.8 A. quadrimaculatus 1,6 0.5 0o5 0,4 1,8 2.8 5,6 A, walkeri 0.0 0.0 0.0 0,0 oa 0.4 0,1 Culex apicalis 36,9 40,5 49.3 48,0 43,8 39.1 39,6 C, pipiens 18,9 16.3 18.2 19.4 20*8 22.1 19,2 C. salinarius 2.8 2.3 2 07 1.1 1.5 1.5 OcO C, territans 11.6 10,7 11.0 11.8 10.0 7,8 8.2 Mansonia perturbans 0.4 0.1 0,0 0.01 0.3 0.1 oa Psorophora ciliata 0.0 0.0 0,0 0,0 0,0 0,0 0.17 P, columbiae 0.0 0.0 0.2 0,0 0.0 0,0 0.0 Theobaldia inpatiens 0*0 0,0 0,0 OcO 0.0 0,0 0.0 T, inornata 0.0 0.0 OoO 0.0 0.0 0.0 0,0 T. melanura 0.8 0,2 0.6 1.3 1,3 0,7 0,6 T0 morsitans 0.4 0.5 0.1 0,0 0,7 0.0 0,0 Uranotaenia sapphirina 0,0 2.7 3.7 3.9 4,4 5.0 4.4 Wyeomyia smithii 0,0 0,0 0.0 0.0 0.0 0.0 0.0 107 TABIE XL B SEASONAL DISTRIBUTION DY VTEEKS % of Total Collections Larvae 34- 35 36 r? rj o / 38 39 40 41 42 43 548 353 381 588 902 839 608 365 126 42 0.3 0.5 0,3 0.3 0.1 0.1 0.1 0,2 0.0 0.0 0,0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0,0 0,0 0.1 0.0 0,2 0,1 0.0 0. o 0.5 0.5 0.7 0.0 0.6 0.4 2,5 1.8 1.0 0,5 0.3 0,2 0.4 0.7 0.1 0.2 1.2 0.3 0.1 0,1 0.1 0.0 0.0 0.0 0,0 0.0 0.0 0.0 0,07 0,0 0.0 0.0 0.0 0.0 0.07 0.03 0.05 0.0 0.0 0.0 0.02 0.0 0,07 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 OcO OcO 0.0 0.0 0,0 0,0 0.0 0.0 0.0 0.0 0.0 OcO 0.0 0,0 0.03 0,02 0,0 0.0 0.02 0.0 0.0 0.0 0,0 0.0 0.1 0,1 0.1 0.0 0,0 0.0 0,0 0.0 OcO 0,0 0,0 0.0 0.0 0.0 0.0 0,0 0.0 0.0 0.0 0,7 0.1 1.2 0,4 0,2 0,1 0,0 0.1 0.1 0.1 0,0 0,0 0.0 0.02 0.0 0,0 0.0 0.0 0.0 0,0 0.3 0.0 0,2 0,0 0,0 0.0 0.0 0.04 0.0 0*0 0.0 0,28 0.26 0.0 0.0 0.0 0.0 0.0 OcO OcO 0.1 0.1 0,0 0.1 0.0 0,0 0.1 0,0 0.0 0.0 0,18 0.0 0.0 0.0 0.0 0.0 0.0 0,0 00 0,0 2,9 1.0 6.0 1.4 0.3 0.1 0,4 0.7 0*3 0,0 0.0 0.0 0.3 0.0 0.0 0.3 0.0 0 c27 OcO 0.0 0.3 0,1 0.3 0.1 0.1 0.07 0.06 0.04 0.0 0.0 14.5 16,7 15.0 16.7 17,4 15.3 13,8 14.6 10 o 7 6,9 5.6 c .4 6.1 5,5 5.7 5o8 4.1 4,4 1,2 1.1 0.1 0.1 0,0 0.1 0.1 0.1 0.1 0.1 0.1 0.2 38.0 32,7 31,9 29.7 25 a7 24.4 24.4 21.1 11.1 6.9 21.4 24.7 24.6 26.1 28,8 34.4 35.5 38.0 4109 55.4 0.8 1.0 1*0 2,2 1.6 2.8 o c» 5 3.3 3,9 5,9 9,3 7.5 5.8 7.0 7.6 10,8 10.6 6.9 13.7 8,9 0.1 0,0 0,0 0.02 0.0 0.05 0.06 0.5 0,9 4.8 0.18 0,0 0.0 0,0 0.0 0.0 0.0 0.0 0.0 OcO 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0,0 OcO 0.0 0.0 0.0 0.0 0.0 0.0 0,0 0,0 0.0 OcO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0,0 0.0 0.4 0,4 0.3 0.2 0,3 0.7 1.2 0.9 1.7 . 1,9 0,0 0.0 0.03 0.07 0.0 0U02 0.02 0.0 OcO 0,0 2.7 2.4 , 2.0 . 2,0 1.0 0.7 0.4 ■ 0.1 0.1 - 0.0 0.0 0,0 0.26 0.0 0.0 0,0 0.0 0.0 0.0 2.3 108 TABLE XLI A SEASONAL DISTRIBUTION BY WEEKS Number of Collections ADULTS Week of Year 27 28 29 30 31 32 33 Total Collections 296 512 394 515 460 563 585 Aedes atropalpus 0 4 1 4 3 3 4 A, aurifer 31 43 22 23 11 10 4 A, canadensis 31 42 39 31 40 32 20 A, cantator 11 14 10 13 20 19 28 A, cinereus 17 26 13 19 16 21 29 A. dorsalis 0 1 0 2 0 0 0 A, excrucians 22 43 34 39 28 31 25 A. fitchii 8 14 9 7 10 14 7 A, hirsuteron 0 2 0 0 0 0 0 A, implacabilis 1 4 1 3 1 X 0 0 A, intruders 16 17 9 12 6 4 3 A, punctor 0 1 0 0 0 0 0 A, sollicitans 23 23 11 39 50 46 58 A, stimulants 3 6 6 5 3 3 0 A. taoniorhynchus 0 0 0 0 0 0 0 Ac trichurus 0 0 0 0 1 2 0 A, triseriatus 3 6 3 11 9 22 14 A0 trivittatus 0 0 0 0 1 0 0 A* vexans 13 11 18 12 15 38 29 Anopheles crucians 0 0 0 0 0 0 0 A. maculipennis 0 0 0 0 0 2 0 A, punctipennis 1 2 4 3 7 13 18 A. quadrimaculatus 0 2 1 7 6 14 . 27 A. walkeri 0 0 2 2 X 21 ■5 Culex apicalis 2 10 3 16 19 23 26 C, pipiens 9 21 23 48 51 82 81 C, salinarius o Lj 3 5 9 10 25 21 C „ territans 5 9 14 ■a 10 21 20 Mansonia perturbans 87 203 174 196 158 147 151 Psorophora ciliata 0 0 0 0 0 0 0 P* columbine 0 0 0 0 0 0 0 Theobaldia impa'tiens 0 0 0 0 0 0 1 T„ inornata 0 0 0 0 0 1 0 T, melanura 1 3 5 1 0 4 3 T, morsitans 0 0 0 1 1 2 0 Uranotaenia sapphirina 0 1 1 0 0 1 3 Wyeomyia*smithii 0 0 0 0 0 0 0 109 TABLE XLI A SEASONAL DISTRIBUTION BY WEEKS Number of Collections ADULTS 54 35 36 37 38 39 40 41 42 45 548 353 381 588 902 839 608 365 126 42 8 0 7 11 5 0 0 0 0 0 1 0 • 0 1 0 6 0 0 0 0 4 5 3 3 4 3 6 2 0 0 15 4 21 29 141 118 94 36 4 0 18 10 8 8 22 16 8 4 1 0 0 0 • 0 0 0 0 0 0 0 0 7 2 4 1 2 0 0 1 0 0 4 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 2 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 77 44 74 112 136 111 62 53 0 0 1 0 0 1 1 0 0 0 0 0 0 1 0 6 3 11 0 0 0 0 0 0 0 0 0 0 0 0 0 0 22 15 13 34 4 4 1 2 1 0 0 1 0 0 1 0 0 0 0 0 27 28 40 62 70 67 31 12 3 2 0 0 0 0 0 0 0 0 0 0 2 0 1 0 1 0 0 0 0 0 27 14 12 9 16 20 23 16 8 22 42 12 16 5 8 11 17 11 2 2 9 3 • 0 0 2 0 4 0 0 1 27 32 34 52 164 161 88 70 14 4 100 84 71 122 162 180 163 - 84 59 15 21 13 25 35 45 41 56 48 11 5 42 29 39 35 47 47 66 25 13 1 103 50 11 12 4 6 3 7 1 7 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 • 0 1 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 8 4 • O C 11 0 1 4 3 1 2 0 1 0 0 0 0 0 0 0 0 1 0 4 1 2 2 0 0 0 0 0 0 0 ■ 0 0 0 0 0 0 0 110 TABLE XLI B SEASONAL DISTRIBUTION BY WEEKS % of Total Collections ADULTS Week of Year 27 28 29 30 31 32 33 Total Collections 296 512 394 515 460 553 585 Aedes atropalpus 0.0 0.8 0.3 0.8 0.2 0.5 0.7 A. aurifer 10.5 8.4 5.6 4.5 2.4 1.8 0.7 A. canadensis 10.5 8.2 9.9 6.0 8.7 5.8 3.4 A, cantator 3.7 2.7 2.5 2.5 4.4 3.4 4.8 A. cinereus 5.7 5.1 3.3 3.7 3.5 3.8 5.0 A. dorsalis 0.0 0.2 0.0 0.4 0,0 0.0 0.0 A. excrucians 7.4 8.6 8.6 7.6 6.1 5.6 4.3 A. fitchii 2,7 2.6 2.3 1.4 0.7 0.7 0.3 A. hirsuteron 0.0 0.4 0.0 0.0 0.0 0.0 0.0 A, implacabilis 0.34 0.78 0.25 0.58 0.22 0.0 0.0 A. intrudens 5,4 3.3 2.3 2.3 1.3 0.7 0.5 A, punctor 0.0 0.2 0.0 0.0 0.0 0.0 0.0 A, sollicitans 7.8 4.5 3.1 7.6 10.9 8.3 9.9 Ao stimulans 1.0 1,2 1.5 1.0 0.7 0.5 0.0 A, taeniorhynchus 0.0 0.0 0.0 0.0 0.0 0.0 0.0 A. trichurus 0,0 0.0 0.0 0.0 0.2 0.3 0.0 A. triseriatus 1.0 1.2 0.8 2.1 2,0 4.0 2.4 A, trivittatus 0.0 0.0 0.0 0.0 0.21 0.0 0.0 A. vexans 4.4 2,2 4.6 2.3 3,3 6.9 5.0 Anopheles crucians 0.0 0.0 0.0 0.0 0.0 0.0 0.0 A, maculipennis 0.0 0.0 0.0 o.o- 0.0 0.4 0.0 A. punctipennis 0.3 0.4 1.0 0.6 1.5 2.4 3.i A. quadrimaculatus 0.0 0.4 0.3 1.4 1.3 2.5 4.6 A. walkeri 0.0 0.0 0.5 0.4 0.2 3.8 0.9 Culex apicalis 0.7 1.9 0.8 3.1 4.1 4.2 4.4 C. pipiens - 3.0 4.1 5.8 9.5 11.0 14.8 13.? C* salinarius 0.7 0.6 1.3 1.7 2.2 4.5 3.6 C. territans 1.7 1.8 4,8 1.6 2.2 -3.6- 3.4 Mansonia perturbans 29.4 39.7 44.2 38.0 34.4 26.6 25.8 Psorophora ciliata 0.0 0.0 0.0 0.0 0.0 0.0 0.0 P, columbine 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Theobaldia impatiens 0.0 0.0 0.0 0.0 0.0 0.0 0.17 T. inornata 0.0 0.0 0.0 0.0 0.0 0.2 0.0 T. rnelanura 0.3 0.6 1,3 0.2 0.0 0.8 0.5 T. morsitons 0.0 0.0 0.0 0.2 0.2 0.4 0.0 Uranotaenia sapphirina 0.0 0.2 0.3 0.0 0.0 0.2 0.5 Wyeomyia smithii 0.0 0.0 0.0 0.0 0.0 0.0 0.0 TABLE XL I B DISTRIBUTION BY VtfEEKS %_ of Total Collections ADULTS tO CM I ° o o o o o o o o o o o o o o o CJ ° o o 15 CM o o o o o o o LO rH CJ o • J CJ o c- O CJ rH o 18 tr- 1—1 LO to o o o o o o o o o It- CO CM iO G) o CM o o o CM o 1—1 CM o o CO o IO o o to 05 o 05 CO o CJ o o o o CM 05 o CM o to CO • © ) 0 • o • • • o o © © o > 9 V* • 0 • 0 © o « * 0 o 0 0 0 O r> LO o o •rjH rH o o to o o CJ o o 05 rH o t-l O LO o o «—I CJ 1—i o o CO o CM 0 o w • • cf~ © to 0 to CD to 05 o o o o LO o CM o LO rH o o CM to o rH d d o o o ?cr31 This species was -*iet numerous in August and September,This seasonal prevalence coincides with that of the disease. As in the case of Aedes cantator, the geographical limitation of this mosquito was not the some as that of the disease in 1938, However, mosquitoes were much more prevalent during the outbreak, and wind-borne adults may have been carried inland by the prevailing southwest winds. These species, Aedes cantator and Aedes vex- ans are probably the most likely natural vectors of equine encephalomyelitis. Percent Figure XV] AEDES SOLDICITANS SEASONAL DISTPfBUTIOl By Percent of Total Weekly Collections [assachusetts 1939' i Adults larvae k4ir_J IlOo of week of year ledes stimulans This mosquito is not known to transmit disease; it is not a fierce biter and is numerically unimportantc Larvae were collected in scattered areas throughout the state. Adults were captured on man in two a collection was made in a stable and in a house. This species predominates in the spring and by August is quite rare* Aedes taeniorhynchus This southern salt marsh mosquito is a vector of equine encephalcmyelitis, It is a fierce biter but occurs in such small numbers and is so limited in geographical distribution that it is not of any great public health importance. Its collection was limited to the island of Martha’s Vineyard and to the Buzzard’s Bay region of southern Massachusetts0 Larvae were found in marshes and swamps. Since most of the adults were 120 captured on man, this species probably does not frequent houses. The adults were captured in August and September and it is apparent that the species is most numerous at this time. It is very unlikely that Aedes taeniorhynchus played a role in the 1938 outbreak of equine encephalomyelitis, unless its distribution extended further northward in 1939 than it did in 1938, Figure XVII AEDEG TAEI'l I ORHYNC HU S SEASORAL DISTRIBUTION By Percent of Total Weekly Collections Massachusetts 1939 Percent Adults ..arvae July August September Octob Ho, of week of year Aedes trichurns This is a rare species which is unimportant as a nuisance and as a public health menace.. This mosquito was collected so infrequently that no conclusions concerning its life habits can be made. It is probably an early mosquito with a spring predominance^ Aedes triscriatus Laboratory experiments have demonstrated that this spocies can transmit equine cncepnalomyclitis• It was found bo be sbatc-wiac in distribution but was loss numerous than Aodos voxans which is another vector of this disease. The larvae wore collected from wo3.1s, dumps and' water troughs. Adults wero captured in houses more frequently than on man. Collections were made as frequently in thickly settled areas as in rural sections. The species was most numerous in August and the first throe weeks of September but decreased rapidly during the last week of September, fi&usJSQil. AEDL3 TRI3EPJATUS SP A.3 OPAL DISTRI BUT I ON By Percent of Total Meekly Collections Massachusetts 19S9 Percent Adults arvs No, of week of year Aedes trivittatus This is a rare species of very little importance; Aedes trivittatus larvae were collected in two towns and adults in three. Since 122 Aedes vexans This species, a demonstrated vector of equine encephalo- myelitis, is state-wide in distribution and one of the most numerous of the vectors. The larvae are' ubiquitous in their breeding habits; collections were made from marshes, swamps, ponds, lakes, streams, rivers, cranberry bogs,, puddles, dumps, barrels, a water trough, a well and a rocky crevice. The adults are fierce biters and were frequently collected on man, in stables, barns and in houses. Although more collections were made in rural areas, ur- ban communities were not without this mosquito. This species was collected more frequently in barns and stables than any other Aedes, It was also cap- tured in the vicinity of horses, mules, cattle, and many kinds of birds,Aedes vexans was most prevalent in August and September. It was present in large numbers in July, and, probably would have been present in larger numbers were it not for the drought in July and June, Figure XIX ANDES YEXfJSS Percent SEASONAL DISTRIBUTION By Percent of Total Meekly Collections Massachusetts 1939 Adults Larvae No, of week of year It is conceivable that this species was involve I in tho 1938 outbreak of equine encephalomyelitis. It is the only numerous vector that was found in all areas where the disease occurredc In fact, its dis- tribution was far more extensive than the area involved In the outbreak. It was tho most numerous of the vectors if the number of specimens is con- and second most numerous on the basis of collections. It is not unlikely that Aodcs voxans may prove po be the most important natural vec- tor of equine encephalomyelitis. Anopheles crucians This species was collected for the first time in Massa- chusetts. The larvae alone were found in four towns, Nc adults were col- lected, In some parts of the south. A, crucians may o.ct as a vector of malaria. However, it is so rare a species in Massachusetts that it is un- important as a vector and as a nuisance. No conclusions on the breeding habits can be drawn from the few collections obtained. Anopheles maculipennis This Anopholine is the second most important vector of malaria in Massachusetts, Since malaria is net a problem at the present time, vectors of malaria are not an immediate concern. This speexes is state-wide in distribution but is numerically unimportant. Of the five Anopheles, it is third in numerical importance. Larvae were collected from rivers and streams, marshes a.nd swamps, ponds and lakes, excavations, a puddle and a water trough. The species breeds principally in sparsely settled areas, A.dult collections were few; seven specimens were captured in houses. The sea.sonal predominance of this species is apparently in- July and August; this observation, however, is based on relatively few collections• Anopheles Dunctipennis Although A, punctipcnnis may transmit malaria experimen- tally, it is not an important natural vector. It is, therefore, unimportant except as a nuisancee It is by far the most numerous Anopholine, and was collected in most of the cities and towns in rlassachusetts, The larvae arc ubiquitous in their breeding habits as can be seen from the list of breed- ing places. In this respect, it resembles C. apicalis and C. pipiens. Fre- quently the adults were captured in houses. Some were caught on nan and a few in stables. Although more numerous in rural sections, urban commun- ities were not free of them, Tho species continues at about the same level throughout the mosquito season, with a tendency to increo.se, until tho onset of cold weather. The sudden rise in adults during tho second half of Octo- ber, is probably due, not to an actual incrco.se in the species, but to tho small number of total collections of adults. Anopheles quadrimaculatus This mosquito is tho important malarial vector in the Uni ted States,. It is an avid biter and was collected from all sections of the state. The larvae breed ubiquitously. Most productive breeding places were rivers and streams, ponds and lakes and marshes and swamps. The adults wore collected in densely as well as sparsely populated areas. Many adults were captured in buildings, some in barns and a few on man. This species was most predominant during August and September. Few were found in July, due no doubt to the lack of rain. As the chief vector of malaria, A. quadrimaculatus is a concern of the public health official. However, at the present time, mal- aria is rare in Massachusetts and there is no apprehension over this vec- tor’s wide geographical distribution. Anopheles walkeri Duo to its small numbers, A. walker! is unimportant as a vector of malaria. It was collected throughout the state. The larvae were found from July through October, Most of those were collected at other than regular collection points. The adults were captured in houses and in the vicinity of stables, horses and mules. The seasonal distribution of this species cannot be determined from the collections, but most of the adults wero caught in August, The apparent increase cf adults late in October may bo due to the small number of collections made at that time. Culox apica1i s Because this species is known not to bite man it has no public health importance. C. apicalis and Co pipicns arc the two most nu- merous mosquitoes in the state. The former breeds anywhere and everywhere and was collected from all typos of breeding places, often in association with other species. It is found in rural and urban sections, Adults enter houses in large numbers, and a few adults wore caught in stables and barns. Six specimens were captured on man. The larvae were most numerous in July and gradually do- croased as the season advanced. The adults, however, increased as the sea- son advanced.- They apparently survive until the advent of cold vie at her, Culox nipiens As the most numerous species in the state and as a vicious biter, C, pipicns is a nuisance in many parts of the Commonwealth, It was collected from almost every town and city. Larvae arc ubiquitous and breed in all typos of breeding places, appearing in successive broods throughout the season. The adults were so numerous that they wore captured everywhere, G. pipiens was collected in houses, in barns and in stables more often than ether species. It will bite man in the open,. The species steadily increased in number throughout the season but was most prevalent in September and Oct- ober, Experimental transmission of equine encephalomyelitis has been unsuccessful with this species; hence, C, pipicns is important only as a nuisanco. Culex salinarius This mosquito is important only as a nuisance. It is far less numerous than C, pipiens, Its geographical distribution is state-wide. The larvae were collected from all types of breeding places in both rural and urban sections. Adults were frequently captured in houses, seme were caught in barns anri stables, and a few on man in the open. Like C, pipiens this species continued to increase in numbers as the season advanced. Col ■ lecticrs were most frequent in late September and October. Culex territans Except as a nuisance this mosquito is of no importance* It was collected throughout the sbate. The larvae are almost as ubiquitous as those of C, pinions and breed in many different types of water. Collect tions were maoe*~in"T>oth rural and urban communities. Adults were frequently captured in houses, a few were caught on man, and occasional collections wen made in barns and stables. There was no definite seasonal predominance, Th species was numerous at all times although adults increased with the advance of the season. Mansonia perturbans This mosquito is a fierce biter and was the cause of many complaintso It is state-wide in distribution and is important because of its large numbers. The larvae, which attach themselves to water plants, were collected in small numbers. The adults wore caught in houses and in barns and stables almost as frequently as C, pipiens, and during the spring and early summer were a chief nuisance indoors. They were captured more often on man than any other species except A, sollicitans. This species cannon transmit equine encephalomyelitis in the laboratory and, hence, is of im- portance only as a nuisance. There was a definite seasonal predominance; the adults were most numerous in July, and gradually decreased in number thereafter. Orthopodomyia signifera Larvae of this species were collected in the town of Sud- bury from a wooden barrel containing rain water, Several collections were made during the 32nd week (August 6-12). This is the first time this genus was recorded from Mass- achusetts, It is cf no importance, as it is not known to bite man and is very rare. Psorophora ciliaxa This species is one of the largest mosquitoes of Massachu- setts and is a. fierce biter. It is rare and was collected only in the Conn- ecticut River Valley and on Martha’s Vineyard, a large island south of Capo Cod.Because of its small numbers it is of no importance as a nuisance,It is not 126 known to transmit disease. The adults were captured in June and August and the larvae in July. Psorophora columbiae "~0nly larvae were collected of this species. It is said to be a fierce biter but is too rare to be of any public health importance. The larvae were collected in Hampshire County in July and August. This species was reported from Massachusetts by Johnson in 1S25. It is rare and was not collected during the Survey. It is said to be a severe biter. Psorophora posticata Theobaldia imnatiens The genus Theobaldia is rare in Massachusetts. It was col- lected in this state fer the first time during the Survey. Two collections of adults were made in northern Massachusetts in August and the other in Sep- tember. No larvae were found. This species is said not to be a persistent biter, and is of no public health importance. Theobaldia inornata Three collections of adults were made of this rare species. The specimens were captured in August and September, No larvae were found. It is of no public health importancec Theobaldia melanura ~0f the genus Theobaldia, this species is most numerous. It was collected throughout the state'. Larvae were found in largest numbers in marshes and swamps, ponds end lakes, rivers and streams and root holes in sparsely settled areas. Both adults and larvae wore found throughout the sea- son, Adults were captured on man and also in buildings. The apparent in- crease in adults late in October consisted of only two collections, which, however, represented 4,8% of the total,. This number is too small to be sig- nificant. This species is not a vicious biter and has no public health im- portance. Theobaldia morsitons ■*——* This mosquito is rare in Massachusetts and is unimportant as a nuisance. It was collected in small numbers throughout the state. Lar- vae were collected most frequently in cranberry bogs. The adults were col- lected only once in a house. Collections were too few to furnish information as to the habits and seasonal prevalence. This species is not known to trans- mit disease * Uranotaenia sapphirina Being the only species of this genus in Massachusetts, this mosquito is unimportant as a nuisance and is not known to transmit disease,, It is state-wide in distribution. Larvae were collected most frequently in marshes, swamps, ponds, lakes, rivers and streams in rural areas.- The adults were captured less often than the larvae and were not found to bite man or to enter houses. The larvae were most numerous in August, whereas the adults were captured too seldom to give an indication of their seasonal prevalence. YJyeomyia smithii A very rare species, W, smithii is of no importance except to the entomologist. The larvae were collected at the tip of Cape Cod and the adults in the Berkshires, This species breeds in pitcher plants and is difficult to collect,' It, no doubt, breeds in many marshes and swamps where pitcher plants abound0 Chaoborus Suedes The sub-family Chaoborinae consists of several genera of mosquitoes whose proboscis is not adapted for bloodsucking. The larvae of these mosquitoes are predatory and are of importance only in that they may destroy the larvae of the Culicinao, or biting mosquitoes. However, this method of natural control is not very effective and all the Chaoborinae arc of little importance except to entomologists. The species of the various genera were not routinely iden- tified, Chaoborus is a genus which is state-wide in distribution. Adults and larvae were collected throughout the duration of the Survey, Corethrella Corethrella is another genus of the sub-family cf Chaobor- inae, the non-biting mosquitoes. It is, therefore, of no import an ce~"except as a predator on other larvae. Mosquitoes in this genus were not routinely identified by species. One species C„ brakeleyi is reported here for the first time in Massachusetts, Collections in eastern Massachusetts wore limited to larvae during July and September, Dixa Species This genus of non-biting mosquitoes is the most numerous of the Chaoborinae whose larvae are predatory on other mosquito larvae* It is state-wide in distribution. Larvae were collected from rivers and streams and from still water. Adults were collected only twice in southern Massachu- setts, Collections were most numerous in August and September, Because of the small numbers of all the Chaoborinae. their predatory habits have little effect in the natural control"of the Culicinao. Eucorethra underwood! As a non-biting mosquito this species is important only as 128 a predator on the larvae of other species. It is rare and was collected in two places; Savoy in the Berkshires and Yarmouth on Cape Cod, The lar- vae were collected in streams. No adults were found. Mo chionyx Species This genus belongs to the sub-family Chaoborinae which are non-biting mosquitoes. Except as a predator in the larvae of bitTng mosqui- toes, it has no importance. This genus was collected in Barnstable,, Dukes and Plymouth Counties, all in southeastern Massachusetts. Only larvae "were collected in both running and still water. BIBLIOGRAPHY Johnson, C. We; Fauna of New England, Boston Society of Natural History, Boston, Mass, 1925 Matheson, Robert; The Mosquitoes of North America, C, C. Thomas, 1S29 CHAPTER XVI CONCLUSIONS ON THE MOSTTITO TRTiSiTSSiON OF Errors’ ~ Epidemiological investigations have supported the laboratory ob- servations that mosquitoes are capable of transmitting equine encephalomy- elitis, Field observations reveal the confirmatory evidence that mosquitoes are abundant during outbreaks of this disease. During the Massachusetts epidemic of 1938, mosquitoes were observed to be unusually numerous in the. same area where the disease was prevalent. It was observed that the disce.se moved, principally to the northeast, in the direction of the prevailing windsj and, it has been postulated, that mosquitoes were carried by these winds, thereby causing a rapid spread of the disease. Data, collected by the Survey, has furnished additional epidemi- ological support to the mosquito transmission of equine encephalomy- elitis . 1, Seasonal Prevalence of Vector and Disease Correspond For the effective transmission of a mosquito-borne disease, there must be a certain minimal numerical ratio between the vector, host and would-be host0 Then the vec- tors are unusually prevalent, this ratio rises, and conditions for increased transmission arc present. In 1938, the outbreak reached a peak in late Au- gust and early September, In 1959, the seasonal prevalence of mosquitoes was determined. Thereas the genus Acdos was more abundant in spring and early summer, the vectors, Acdos atropalpus, A. cantator. A, sollicitans, A. tac- niorhynchus, A. triscriatus and A, vexans were most numerous in August and September, The seasonal prevalence of the vector and of the disease corres- pond. Therefore, conditions most conducive to the transmission of the virus exist in the late summer and early autumn. The unusual abundance of mosqui- toes in 1958 provided optimal conditions for the outbreak. 2, Geographical Distribution is the Seme The vectors of equine cnccphalo- myc1'itis wc:rc~prcTsbn^"irT*tlTel^TTrcfls" where, formerly, the disci’sc was pres- ent, Four of the vectors. A, sollicitans. A, cantator, A. vexans and A.tri- soriatus were found in the area whore most of the eases existed. Only two vectors. A, voxans and A. triscriatus were present in all places where cases occurred, A. triscriatus, however, was found to be only l/5th to 1/15th as numerous as A, vexans , "Therefore, statistically, it seems that A, vexans is the most important vector of equine encephalomyelitis. 3. Acdcs vcx'mis is the Most Probable Natural Vector Further confirmatory evidence in the support of A, vexans ns the vector is found in the distri- bution of equine encephalomyelitis eases in 1939. Twelve cases, which are spotted on I,lap V , were diagnosed by the Massachusetts Department of Agri- culture. Although most of these were diagnosed on clinical findings, the virus was isolated from the brains of two horses which had lived and died in the towns of New Braintree and Acstborough, These towns are so far in- land that no salt marsh mosquitoes were collected and the probability of a mosquito of this group infecting these horses is negligible. The nearest brooding place of the salt marsh vector was twenty miles from TTestborough MAP V CASES OF EQUINE E N C E P H A LO MYELITIS MASS AC H USE ITS 19 3 9 LEGEND •MAN - HORSE and over fifty miles from Hew Braintree, Fifteen miles away from their breeding places is the greatest distance at which the adult salt marsh mosquitoes, A. sollicitans and A. cantator, were collected. Lhcn wind- borne, both species have been recorded to fly farther. Here, however, the prevailing winds in the summer and early autumn blow from the west and southwest, Galt marsh mosquitoes would have to fly against the wind for twenty to fifty miles to roach these two towns. Furthermore, long flights of salt marsh mosquitoes are a rare phenomenon, so, statistically, the chances of a few adulvs surviving such long flights arc almost negligible, Alltheso facts point to a mosquito other than the salt marsh Aodes as the carrier. On]y two vectors were found in this area. A, triseriatus said A. vexans. Since A, vexans is five to fifteen times as numerous as the for- mer, statistically, A. Vexans is the most probable vector responsible for the infection of those horses. 4, Age Distribution of Cases is Explained by the Bionomics of Vectors The termination of the bionomics of the vectors of equine encephalomyelitis of- fers explanations of several Phenomena observed in the 1238 outbreak. Twenty- six percent of the cases in man were infants under one year of age, and twen- ty percent were children under ten. Although detailed information about in- dividual cases has not been obtained, the high attack rate among the younger age groups may be explained by the following observations. During the sum-' mcr, infants are often left to sleep outdoors, sometimes without protective netting, and are unable to defend themselves against mosquitoes. Moreover, children under ten who play outdoors the greater part of the day arc less ef- ficient than elder groups in protecting themselves as they do not.react to a mosquito until it has bitten thorn. Thus, indications are that infants and children who sleep or play outdoors are more apt to bo bitten than older in- dividuals who, taught by experience, react to the buzzing or alighting of a mosquito. Of all mosquitoes captured on non outdoors, sixty percent wore vec- tors, while only six percent cf those caught indoors were carriers. There- fore, the chances are throe out of five that a mosquito which has bitten an individual in the open is a vector, while indoors the chances are three out of fifty that the biting mosquito is a carrier. These findings explain why infants and children comprise such v high proportion of the cases. 5. Vectors Bite Horses Outdoors It was observed that horses which spent the greater part of their existence outdoors, formed the larger portion of the cases. Data collected during the Survey indicates that the vectors are mere likely to bite in the open rather than indoors. Hence, horses which are out- doors arc more apt to bo infected. 6. Summary of Conclusion The summation of these facts establishes the the- ory of the mosquito transmission of equine encephalomyelitis on an epidemiol- ogical basis. Laboratory experiments have demonstrated mosquito transmission of the disease. The combined evidence of the laboratory and the field is tantamount to proof cf this theory. Although some individuals may not con- sider necessary the finding of a mosquito which is naturally infected with the virus cf equine encephalomyelitis, this discovery is, nevertheless, a logical sequel to the experimental work in the proof of this theory. 132 CHAPTER XVII SUMMARY MOS QUIT0-BORNE DISEASES IN MASSACHUSETTS ?. o Various investigators have observed that mosquitoes were abun- dant during outbreaks of equine encephalomyelitis and suggested that the di- sease may be mosquito-borne. Experiments conducted in several laboratories have demonstrated that certain Aedes mosquitoes can transmit the disease. The theory of mosquito transmission was, thereby, established upon expermen- tal evidence but needed further epidemiological confirmation. 2„ During August and September of 1S58, an outbreak of the eastern variety of equine encephalomyelitis in southeastern Massachusetts reached a peak. About three hundred horses succumbed to the disease. In men there were thirty-four cases, 26%, of which were infants under one year of age and 70% were children under ten. The disease ran a rapid fulminating course with a case fatality of 74$. A follow-up of the eight survivors one year later, re- vealed the presence of sequelae in 85%, Sc The Mosquito Survey was organized by the Massachusetts Depart- ment of Public Health in cooperation with the Work projects Administration to determine :,the prevalence, and seasonal and geographical distribution of mosquitoes throughout the Commonwealth”, and to ascertain the relationship of these insects to equine encephalomyelitis and other mosquito-born© dis- eases . 4a At the present time, malaria is the only other mosquito-borne disease in Massachusetts0 Three epidemic waves have spread over the state in the past 150 yearsc Twenty-five years ago, malaria was endemic in three areas in the state. During the past ten pears, however, there were only eleven cases which were naturally acquired within the state. Although malar- ia is not prevalent now, it may be reintroduced and become a serious problem 5U Several other mosquito-borne diseases may be introduced into Massachusetts, namely, yellow-fever, which was epidemic here in the' 18th cen- tury, dengue and filariasis, both of which are endemic in the south. Two diseases suspected of mosquito transmission which may become local problems are St. Louis encephalitis, which has not been reported in this state but which is widespread throughout the United States, and lymphocytic choriomen- ingitis, which is being diagnosed in Boston at this time. Formerly, poliomy- elitis was suspected of being spread by mosquitoes, but evidence indicates that it is net transmitted in this manner. 6, The most effective control of mosquito-borne disease is the control of vectors. Some measure of control may be obtained by the immun- ization of susceptibles, as in yellow fever. With the exception of the vac- cine for the protection of horses against equine encephalomyelitis, this meth- od is not applicable to other mosquito-borne diseases. Control of these dis- eases, therefore, depends upon effective control of the vectors. However, be- fore a mosquito control program is launched, data on the bionomics and the seasonal and geographical distribution of the vectors must be obtained by a survey. THE ADMINISTRATION OF THE MOSQUITO SURVEY 7. In 1939 from June to November inclusive, tho Survey was made throughout the state. One hundred seven Work Projects Administration col- lectors and volunteer collectors solicited through the cooperating local boards of health, submitted 278,887 specimens in 49,251 collections. An office personnel of thirty-two Work Projects Administration employees ad- ministered the Survey and prepared tho report. The field and office person- nel was under the direction of a project supervisor. Nine entomologists employed by the state, made special collections, identified the specimens and assisted tho technical director of the Survey in supervising, directing and administering the Survey, 8. Work Projects Administration supervisors, foremen and as sistent foremen, and the heads of the various office departments were given a one week training in a course consisting of lectures, laboratory exercises and field trips, Tiiesc individuals, in turn, trained members of their crews in the recognition and collection of mosquitoes, A bulletin entitled nTraining Course for Field Personnel" containing the lecvurcs given during this week was published by the Survey. 9. The field personnel consisted of five supervisors who directed twenty crews distributed throughout the state and averaging five men. Each crew was provided with two automobilesj one was used by the foreman to visit boards of health and groups of volunteer collectors, while the other was used to transport tho crew. The plan of the Survey called for weekly collections in every town in the state. Therefore, each crew was given a schedule which provided for collections in each town to be made by one man, one day each week. The crew members wore transported to the towns where they walked be- tween the collection points, au the end of the day they were not by tho auto- mobile at a designated place and brought back to the headquarters. 10. In order to obtain data on the ecology and bionomics of mosqui- toes, collections wore made weekly at regular collection points. The collec- tion point was defined as an area with a radius of one hundred yards. These points wore spotted on maps and surveyed on special forms. Labels accompanied each collection, and contained information on conditions at the time of the sampling. 11. Special collections were made with light and animal-baited traps on farms where cases of equine encephalomyelitis were reported. Unfortunately due to adverse conditions, small numbers of mosquitoes wore collected, and no true sampling of the mosquito fauna was made in tho environment of cases. 12, Permanent collections of larvae, adults and hypopygial mounts were prepared, A new key for the identification of mosquitoes was published in Psyche 46: 115-136, December 1939. 13. Tho data gathered by the Survey was summarized on special forms, and then analyzed on the ninety-hole punch card. Two sots of cards were used. One set consisted of data assembled from regular collections, and was used to obtain facts on the bionomics said ecology of mosquitoes. The second set con- tained all the data collected in the Survey, and was used to determine the 134 prevalence, and seasonal and geographic distribution of the different spe- cies O 14, Numerous bulletins were released during the Survey, including the training course for collectors, and a series of pamphlets entitled '’Mass- achusetts Mosquitoes”„ The objectives of these publications -were to; 1. Promote the enrollment of volunteer collectors, 20 Inform all collectors how to distinguish mosquitoes from related insects, and how to collect larvae and adults0 3, Impart information about mosquitoes to the public. 4, Report the results of the Survey. 15. Material for a series of public exhibits on mosquitoes and their relation to disease were prepared by the Survey. These exhibits are being displayed at the Food and Drug Show, The New England Museum of Natu- ral History, the annual convention of the Massachusetts Medical Society and the Eastern States Exposition. LIASSACIiUSSTTS MOSQUITOES 16e Collections of mosquitoes were made without selection, so as to have a true sample of the mosquito fauna*. There was no significant as- sociation between the sizes of the communities, both in area and population, and the number of collections. The average number of collections per town was 106, and the average per square mile was nine* Over 8d;b of the collec- tions were made by the Survey personnel. 17, The effect of meteorological conditions upon the prevalence of mosquitoes may be summarized as follows; 1, Increased rain results in increased prevalence about twe weeks la- ter. 2, The accumulation of excess degree days of temperature results in in- creased prevalence, 3, The prevailing winds from the south and southwest carry adults from salt water breeding places inland to the east and northeast, 40 The peak of the 1938 outbreak of equine encephalomyelitis occurred about four weeks after rein. This interval of time is sufficient for mosquitoes to develop, become infected, undergo an extrinsic incubation period, and infect horses, which become ill in three or four days c 18, The collections of larvae from different types of breeding places was unselected, and consisted of true sampling. There was no sta- tistical significant difference in the number of species breeding in the various types of places. Collections of larvae were most numerous from rivers, streams, ponds, lakes, marshes and swamps. The occurrence of the various species in twenty types of breeding places is described in detail* 19c The vast majority of adult mosquitoes were collected by placing the killing tube over the resting insect rather than by sweeping with the not* Of the 1,977 mosquitoes caught on man outdoors, Aedes sollicitans was the most numerous. The vectors of equine encephalomyelitis comprised 59,9/o of those specimens. Of a total of 3,130 adults captured in houses, Culox pipiens was the most numerous, and the vectors of equine encephalomyelitis comprised only 135 6% of the total. Only 211 specimens were collected in barns and stables; mere, Culox pipions was tho most numerous, and the vectors of equine en- cephalomyelitis comprised about 16%. 20. Of the six vectors of equine encephalomyelitis,Aedos cantator A, sollicitans and A. vexans each constitute about 30%, and A, "atropalpus, A. triseriatus and A, taoniorhynchus together comprise 10%, The prevalence of vectors in the counties varied significantly. Vectors constituted over 75% of tho adult mosquitoes captured in Dukes County, 21 to 30% in Barnstable, Essex and Norfolk Counties, 11 to 20% in Bristol, Franklin, Hampden, Plymouth and Suffolk, and 1c ss than 10% in Berkshire, Hampshire, Middlesex and Worces- ter Counties. Vectors comprised 25.6% cf the total adult collections in the state. In the coastal areas. A, sollicitans was usually the most numerous vector. In all other parts of the state A. vexans wa.s the or eve. i ling vector, and from five to fifteen times as numerous as other vectors. 21o There arc five Anopheles mosquitoes in Massachusetts, all of which may act as vectors of malaria, M quadrimaculatus, however, is the on- ly important vector, and is s A punctipennis is the most numerous, and, because of its large numbers, nay play a roTe'Tn tho transmission of malaria. A. maculipeimis is much less numerous. A, walkeri and A, crucians are both rare. Whoreoafon!y 0.,5%, of the adults captured on man outdoors were Anopheles, 16% of those caught in houses vere malaria vec- tors. Anopheles enter houses much more frequently then Acies, 22. In Massachusetts, there arc nine genera of Culicinae and five of Chaoborinac. The former are provided with a proboscis for bloodsucking and contain forty-one species' throe. Anopheles crucians, Psorophora Colum- and Thoobaldia inpations wore collected by tho Survey for th* first tine in Massachusetts, The Chaoborinae arc important only because their larvae are predatory on these cf other species. There are fifteen species of these non-biting mosquitoes in this state. All of them are rare and, hence, unim- portant as a method of natural control of mosquitoes. Two species, Eucorethra under woedi and Corcthrolla brakeleyi were found by the Survey for the first time in Massacnusotts, The prevalence, seasonal and geographical distribution, bionomics of larvae and adults, and the public health importance of each sne- cies is discussed in detail.. The following table lists the species of Massa- chusetts mosquitoesc 23, The; epidimiological and ent one logical data collected by this Survey supports the laboratory evidence that equine encephalomyelitis, is trans- mitted by mosquitoes. The occurrence of the disease, and the vectors in the sane area, has been established. The seasonal prevalence of the disease and the vectors has been found to be the sane. The bionomics of the vectors have been studied,and it has been ascertained that vectors of equine encephalomyel- itis prefer to bite nan and animals outdoors rather than in buildings,Some of the observations made during the 1938 outbreak are explained by these findings. Snail children and infants, who comprised 70% of the cases, are that portion of the population which, during summer, spends a large portion of its time out- doors and, at the same time, is least able to protect itself from mosquitoes. It is to be expected that this group would be bitten more often by the vectors which were collected on nan outdoors ten times as often as they were caught in 136 houses„ The nosquito transmission of equine encephalcnyolitis is, thus, firmly established on a laboratory, epidoinio1o g i cal and entomological basis. The proof of this theory nay not be obtained for many years, but the find- ing of a mosquito naturally infected with the virus of equine encephalomyel- itis, although considered unessential by some, is the logical and conclusive sequel in this chain of evidence. T ABLE XU 11 SimvBY of MOSQUITOES OF MAS SAC Elf 0 ETTS ADULTS LARVAE No a of No. of No. of No „ of Specimens Collections Specimens Collections SUBFAMILY CULICINAE A.edes at r opal pus 60 41 995 AL aurifer 542 186 0 0 A0canadensis 770 301 495 122- A.cantator 1326 599 2704 399 A.cinereus 471 256 482 12] A. communis* 0 0 0 C A,dorsalis 4 4 79 14 A,excrucians 485 268 41 15 A.fitchii 196 95 21 5 A.hirsuteron 7 4 4 4 A imp1a cab i1i s 29 16 10 3 A.impiger* 0 0 0 0 A.intrudens 29-5 131 48 8 A.punctor 6 5 0 0 A.sollicitans 2548 802 1054 145 A.stimulans 59 38 8 2 A.taeniorhyrchus 20 18 112 17 A.trichurus 20 8 2 2 A ctriseriatus 228 159 92 33 A.trivittatus 6 3 1 1 A.vexans 1052 454 3358 519 Total Aedes 8124 3336 9504 1487 Anopheles crucians** 0 0 20 7 A c ma c u1i pennis 30 5 113 58 A,punctipehni s 300 192 20396 5757 A•quadrimaculatus 790 182 6810 1729 A.walkeri 57 28 84 31 Total Anopheles 1177 407 27423 7582- Culex apicalis 1746 688 78944 13051 C .pipiens 3880 1313 103138 11640 C.salinarius 832 339 2215 922 C.territan^ 94-3 398 23353 3527 Total Culex 7401 2738 207650 29140 Mansonia perturbans 6665 1320 662 69 Orthopodomyia signi- fera** 0 0 3 1 Psorophora ciliata 4 4 2 2 Pocolumbiae** 0 0 3 3 P.posticata* 0 0 0 0 Total Psorophora 4 4 ' 5 ~5 138 TABLE XU. 11 ~(continued) ADUI ,TS LARVAE U6„ "of " no. of KOo of Uo. of Specimens Collections Specimens Collections SUBFAMILY CUBICIME ~~'Th